WebGPU

Editor’s Draft,

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Abstract

WebGPU exposes an API for performing operations, such as rendering and computation, on a Graphics Processing Unit.

Status of this document

This specification was published by the GPU for the Web Community Group. It is not a W3C Standard nor is it on the W3C Standards Track. Please note that under the W3C Community Contributor License Agreement (CLA) there is a limited opt-out and other conditions apply. Learn more about W3C Community and Business Groups.

1. Introduction

This section is non-normative.

Graphics Processing Units, or GPUs for short, have been essential in enabling rich rendering and computational applications in personal computing. WebGPU is an API that exposes the capabilities of GPU hardware for the Web. The API is designed from the ground up to efficiently map to the Vulkan, Direct3D 12, and Metal native GPU APIs. WebGPU is not related to WebGL and does not explicitly target OpenGL ES.

WebGPU sees physical GPU hardware as GPUAdapters. It provides a connection to an adapter via GPUDevice, which manages resources, and the device’s GPUQueues, which execute commands. GPUDevice may have its own memory with high-speed access to the processing units. GPUBuffer and GPUTexture are the physical resources backed by GPU memory. GPUCommandBuffer and GPURenderBundle are containers for user-recorded commands. GPUShaderModule contains shader code. The other resources, such as GPUSampler or GPUBindGroup, configure the way physical resources are used by the GPU.

GPUs execute commands encoded in GPUCommandBuffers by feeding data through a pipeline, which is a mix of fixed-function and programmable stages. Programmable stages execute shaders, which are special programs designed to run on GPU hardware. Most of the state of a pipeline is defined by a GPURenderPipeline or a GPUComputePipeline object. The state not included in these pipeline objects is set during encoding with commands, such as beginRenderPass() or setBlendColor().

2. Malicious use considerations

This section is non-normative. It describes the risks associated with exposing this API on the Web.

2.1. Security

The security requirements for WebGPU are the same as ever for the web, and are likewise non-negotiable. The general approach is strictly validating all the commands before they reach GPU, ensuring that a page can only work with its own data.

2.1.1. CPU-based undefined behavior

A WebGPU implementation translates the workloads issued by the user into API commands specific to the target platform. Native APIs specify the valid usage for the commands (for example, see vkCreateDescriptorSetLayout) and generally don’t guarantee any outcome if the valid usage rules are not followed. This is called "undefined behavior", and it can be exploited by an attacker to access memory they don’t own, or force the driver to execute arbitrary code.

In order to disallow insecure usage, the range of allowed WebGPU behaviors is defined for any input. An implementation has to validate all the input from the user and only reach the driver with the valid workloads. This document specifies all the error conditions and handling semantics. For example, specifying the same buffer with intersecting ranges in both "source" and "destination" of copyBufferToBuffer() results in GPUCommandEncoder generating an error, and no other operation occurring.

See § 20 Errors & Debugging for more information about error handling.

2.2. GPU-based undefined behavior

WebGPU shaders are executed by the compute units inside GPU hardware. In native APIs, some of the shader instructions may result in undefined behavior on the GPU. In order to address that, the shader instruction set and its defined behaviors are strictly defined by WebGPU. When a shader is provided to createShaderModule(), the WebGPU implementation has to validate it before doing any translation (to platform-specific shaders) or transformation passes.

2.3. Uninitialized data

Generally, allocating new memory may expose the leftover data of other applications running on the system. In order to address that, WebGPU conceptually initializes all the resources to zero, although in practice an implementation may skip this step if it sees the developer initializing the contents manually. This includes variables and shared workgroup memory inside shaders.

The precise mechanism of clearing the workgroup memory can differ between platforms. If the native API does not provide facilities to clear it, the WebGPU implementation transforms the compute shader to first do a clear across all invocations, synchronize them, and continue executing developer’s code.

2.4. Out-of-bounds access in shaders

Shaders can access physical resources either directly (for example, as a "uniform-buffer"), or via texture units, which are fixed-function hardware blocks that handle texture coordinate conversions. Validation on the API side can only guarantee that all the inputs to the shader are provided and they have the correct usage and types. The host API side can not guarantee that the data is accessed within bounds if the texture units are not involved.

define the host API distinct from the shader API

In order to prevent the shaders from accessing GPU memory an application doesn’t own, the WebGPU implementation may enable a special mode (called "robust buffer access") in the driver that guarantees that the access is limited to buffer bounds.

Alternatively, an implementation may transform the shader code by inserting manual bounds checks. When this path is taken, the out-of-bound checks only apply to array indexing. They aren’t needed for plain field access of shader structures due to the minBufferBindingSize validation on the host side.

If the shader attempts to load data outside of physical resource bounds, the implementation is allowed to:

  1. return a value at a different location within the resource bounds

  2. return a value vector of "(0, 0, 0, X)" with any "X"

  3. partially discard the draw or dispatch call

If the shader attempts to write data outside of physical resource bounds, the implementation is allowed to:

  1. write the value to a different location within the resource bounds

  2. discard the write operation

  3. partially discard the draw or dispatch call

2.5. Invalid data

When uploading floating-point data from CPU to GPU, or generating it on the GPU, we may end up with a binary representation that doesn’t correspond to a valid number, such as infinity or NaN (not-a-number). The GPU behavior in this case is subject to the accuracy of the GPU hardware implementation of the IEEE-754 standard. WebGPU guarantees that introducing invalid floating-point numbers would only affect the results of arithmetic computations and will not have other side effects.

2.5.1. Driver bugs

GPU drivers are subject to bugs like any other software. If a bug occurs, an attacker could possibly exploit the incorrect behavior of the driver to get access to unprivileged data. In order to reduce the risk, the WebGPU working group will coordinate with GPU vendors to integrate the WebGPU Conformance Test Suite (CTS) as part of their driver testing process, like it was done for WebGL. WebGPU implementations are expected to have workarounds for some of the discovered bugs, and disable WebGPU on drivers with known bugs that can’t be worked around.

2.5.2. Timing attacks

WebGPU is designed for multi-threaded use via Web Workers. As such, it is designed not to open the users to modern high-precision timing attacks. Some of the objects, like GPUBuffer or GPUQueue, have shared state which can be simultaneously accessed. This allows race conditions to occur, similar to those of accessing a SharedArrayBuffer from multiple Web Workers, which makes the thread scheduling observable.

clarify the mitigations here

In the end, the attack surface for races on shared state in WebGPU will be a small subset of the SharedArrayBuffer attacks.

WebGPU also specifies the "timestamp-query" extension, which provides high precision timing of GPU operations. The extension is optional, and a WebGPU implementation may limit its exposure only to those scenarios that are trusted. Alternatively, the timing query results could be processed by a compute shader and aligned to a lower precision.

2.5.3. Row hammer attacks

Row hammer is a class of attacks that exploit the leaking of states in DRAM cells. It could be used on GPU. WebGPU does not have any specific mitigations in place, and relies on platform-level solutions, such as reduced memory refresh intervals.

2.6. Denial of service

WebGPU applications have access to GPU memory and compute units. A WebGPU implementation may limit the available GPU memory to an application, in order to keep other applications responsive. For GPU processing time, a WebGPU implementation may set up "watchdog" timer that makes sure an application doesn’t cause GPU unresponsiveness for more than a few seconds. These measures are similar to those used in WebGL.

2.7. Workload identification

WebGPU provides access to constrained global resources shared between different programs (and web pages) running on the same machine. An application can try to indirectly probe how constrained these global resources are, in order to reason about workloads performed by other open web pages, based on the patterns of usage of these shared resources. These issues are generally analogous to issues with Javascript, such as system memory and CPU execution throughput. WebGPU does not provide any additional mitigations for this.

2.7.1. Memory resources

WebGPU exposes fallible allocations from machine-global memory heaps, such as VRAM. This allows for probing the size of the system’s remaining available memory (for a given heap type) by attempting to allocate and watching for allocation failures.

GPUs internally have one or more (typically only two) heaps of memory shared by all running applications. When a heap is depleted, WebGPU would fail to create a resource. This is observable, which may allow a malicious application to guess what heaps are used by other applications, and how much they allocate from them.

2.7.2. Computation resources

If one site uses WebGPU at the same time as another, it may observe the increase in time it takes to process some work. For example, if a site constantly submits compute workloads and tracks fences for their completion, it may observe that something else also started using the GPU.

A GPU has many parts that can be tested independently, such as the arithmetic units, texture sampling units, atomic units, etc. A malicious application may sense when some of these units are stressed, and attempt to guess the workload of another application by analyzing the stress patterns. This is analogous to the realities of CPU execution of Javascript.

2.8. Privacy

2.8.1. Machine-specific limits

WebGPU can expose a lot of detail on the underlying GPU architecture and the device geometry. This includes available physical adapters, many limits on the GPU and CPU resources that could be used (such as the maximum texture size), and any optional hardware-specific features or extensions that are available.

This specification is designed with respect to a privacy budget. It allows an user agent to decide how much information about the target system is exposed to the developer, thus mitigating the privacy exposure risks.

User agents can group different platforms into coarse groups, reducing the exposed difference in limits between them. The baseline (guaranteed) limits are also deliberately high enough to allow most application to work without requesting higher limits. All the usage of the API is validated according to the requested limits, so the actual hardware capabilities are not exposed to the users by accident.

2.8.2. Machine-specific artifacts

There are some machine-specific rasterization/precision artifacts and performance differences that can be observed roughly in the same way as in WebGL. This applies to rasterization coverage and patterns, interpolation precision of the varyings between shader stages, compute unit scheduling, and more aspects of execution.

Generally, rasterization and precision fingerprints are identical across most or all of the devices of each vendor. Performance differences are relatively intractable, but also relatively low-signal (as with JS execution performance).

Privacy-critical applications and user agents should utilize software implementations to eliminate such artifacts.

2.8.3. Machine-specific performance

Another factor for differentiating users is measuring the performance of specific operations on the GPU. Even with low precision timing, repeated execution of an operation can show if the user’s machine is fast at specific workloads. This is a fairly common vector (present in both WebGL and Javascript), but it’s also low-signal and relatively intractable to truly normalize.

WebGPU compute pipelines expose access to GPU unobstructed by the fixed-function hardware. This poses an additional risk for unique device fingerprinting. User agents can take steps to dissociate logical GPU invocations with actual compute units to reduce this risk.

3. Fundamentals

3.1. Conventions

3.1.1. Dot Syntax

In this specification, the . ("dot") syntax, common in programming languages, is used. The phrasing "Foo.Bar" means "the Bar member of the value (or interface) Foo."

For example, where buffer is a GPUBuffer, buffer.[[device]].[[adapter]] means "the [[adapter]] internal slot of the [[device]] internal slot of buffer.

3.1.2. Internal Objects

An internal object is a conceptual, non-exposed WebGPU object. Internal objects track the state of an API object and hold any underlying implementation. If the state of a particular internal object can change in parallel from multiple agents, those changes are always atomic with respect to all agents.

Note: An "agent" refers to a JavaScript "thread" (i.e. main thread, or Web Worker).

3.1.3. WebGPU Interfaces

A WebGPU interface is an exposed interface which encapsulates an internal object. It provides the interface through which the internal object's state is changed.

As a matter of convention, if a WebGPU interface is referred to as invalid, it means that the internal object it encapsulates is invalid.

Any interface which includes GPUObjectBase is a WebGPU interface.

interface mixin GPUObjectBase {
    attribute USVString? label;
};

GPUObjectBase has the following attributes:

label, of type USVString, nullable

A label which can be used by development tools (such as error/warning messages, browser developer tools, or platform debugging utilities) to identify the underlying internal object to the developer. It has no specified format, and therefore cannot be reliably machine-parsed.

In any given situation, the user agent may or may not choose to use this label.

GPUObjectBase has the following internal slots:

[[device]], of type device, readonly

An internal slot holding the device which owns the internal object.

3.1.4. Object Descriptors

An object descriptor holds the information needed to create an object, which is typically done via one of the create* methods of GPUDevice.

dictionary GPUObjectDescriptorBase {
    USVString label;
};

GPUObjectDescriptorBase has the following members:

label, of type USVString

The initial value of GPUObjectBase.label.

3.2. Invalid Internal Objects & Contagious Invalidity

If an object is successfully created, it is valid at that moment. An internal object may be invalid. It may become invalid during its lifetime, but it will never become valid again.

Invalid objects result from a number of situations, including:
To determine if a given GPUObjectBase object is valid to use with a targetObject, run the following steps:
  1. If any of the following conditions are unsatisfied return false:

  2. Return true.

3.3. Coordinate Systems

WebGPU’s coordinate systems match DirectX and Metal’s coordinate systems in a graphics pipeline.

3.4. Programming Model

3.4.1. Timelines

This section is non-normative.

A computer system with a user agent at the front-end and GPU at the back-end has components working on different timelines in parallel:

Content timeline

Associated with the execution of the Web script. It includes calling all methods described by this specification.

Steps executed on the content timeline look like this.
Device timeline

Associated with the GPU device operations that are issued by the user agent. It includes creation of adapters, devices, and GPU resources and state objects, which are typically synchronous operations from the point of view of the user agent part that controls the GPU, but can live in a separate OS process.

Steps executed on the device timeline look like this.
Queue timeline

Associated with the execution of operations on the compute units of the GPU. It includes actual draw, copy, and compute jobs that run on the GPU.

Steps executed on the queue timeline look like this.

In this specification, asynchronous operations are used when the result value depends on work that happens on any timeline other than the Content timeline. They are represented by callbacks and promises in JavaScript.

GPUComputePassEncoder.dispatch():
  1. User encodes a dispatch command by calling a method of the GPUComputePassEncoder which happens on the Content timeline.

  2. User issues GPUQueue.submit() that hands over the GPUCommandBuffer to the user agent, which processes it on the Device timeline by calling the OS driver to do a low-level submission.

  3. The submit gets dispatched by the GPU invocation scheduler onto the actual compute units for execution, which happens on the Queue timeline.

GPUDevice.createBuffer():
  1. User fills out a GPUBufferDescriptor and creates a GPUBuffer with it, which happens on the Content timeline.

  2. User agent creates a low-level buffer on the Device timeline.

GPUBuffer.mapAsync():
  1. User requests to map a GPUBuffer on the Content timeline and gets a promise in return.

  2. User agent checks if the buffer is currently used by the GPU and makes a reminder to itself to check back when this usage is over.

  3. After the GPU operating on Queue timeline is done using the buffer, the user agent maps it to memory and resolves the promise.

3.4.2. Memory Model

This section is non-normative.

Once a GPUDevice has been obtained during an application initialization routine, we can describe the WebGPU platform as consisting of the following layers:

  1. User agent implementing the specification.

  2. Operating system with low-level native API drivers for this device.

  3. Actual CPU and GPU hardware.

Each layer of the WebGPU platform may have different memory types that the user agent needs to consider when implementing the specification:

Most physical resources are allocated in the memory of type that is efficient for computation or rendering by the GPU. When the user needs to provide new data to the GPU, the data may first need to cross the process boundary in order to reach the user agent part that communicates with the GPU driver. Then it may need to be made visible to the driver, which sometimes requires a copy into driver-allocated staging memory. Finally, it may need to be transferred to the dedicated GPU memory, potentially changing the internal layout into one that is most efficient for GPUs to operate on.

All of these transitions are done by the WebGPU implementation of the user agent.

Note: This example describes the worst case, while in practice the implementation may not need to cross the process boundary, or may be able to expose the driver-managed memory directly to the user behind an ArrayBuffer, thus avoiding any data copies.

3.4.3. Multi-Threading

3.4.4. Resource Usages

A physical resource can be used on GPU in one of the following internal usages:

input

Buffer with input data for draw or dispatch calls. Preserves the contents. Allowed by INDEX, VERTEX, or INDIRECT.

constant

Resource bindings that are constant from the shader point of view. Preserves the contents. Allowed by UNIFORM or SAMPLED.

storage

Read-write storage resource binding. Allowed by STORAGE.

storage-read

Read-only storage resource bindings. Preserves the contents. Allowed by STORAGE or STORAGE.

storage-write

Write-only storage resource bindings. Allowed by STORAGE.

attachment

Texture used as an output attachment in a render pass. Allowed by OUTPUT_ATTACHMENT.

attachment-read

Texture used as a read-only attachment in a render pass. Preserves the contents. Allowed by OUTPUT_ATTACHMENT.

Textures may consist of separate mipmap levels and array layers, which can be used differently at any given time. Each such texture subresource is uniquely identified by a texture, mipmap level, and (for 2d textures only) array layer, and aspect.

We define subresource to be either a whole buffer, or a texture subresource.

Some internal usages are compatible with others. A subresource can be in a state that combines multiple usages together. We consider a list U to be a compatible usage list if (and only if) it satisfies any of the following rules:

Enforcing that the usages are only combined into a compatible usage list allows the API to limit when data races can occur in working with memory. That property makes applications written against WebGPU more likely to run without modification on different platforms.

Generally, when an implementation processes an operation that uses a subresource in a different way than its current usage allows, it schedules a transition of the resource into the new state. In some cases, like within an open GPURenderPassEncoder, such a transition is impossible due to the hardware limitations. We define these places as usage scopes.

The main usage rule is, for any one subresource, its list of internal usages within one usage scope must be a compatible usage list.

For example, binding the same buffer for storage as well as for input within the same GPURenderPassEncoder would put the encoder as well as the owning GPUCommandEncoder into the error state. This combination of usages does not make a compatible usage list.

Note: race condition of multiple writable storage buffer/texture usages in a single usage scope is allowed.

The subresources of textures included in the views provided to GPURenderPassColorAttachmentDescriptor.attachment and GPURenderPassColorAttachmentDescriptor.resolveTarget are considered to be used as attachment for the usage scope of this render pass.

The physical size of a texture subresource is the dimension of the texture subresource in texels that includes the possible extra paddings to form complete texel blocks in the subresource.

Considering a GPUTexture in BC format whose [[textureSize]] is {60, 60, 1}, when sampling the GPUTexture at mipmap level 2, the sampling hardware uses {15, 15, 1} as the size of the texture subresource, while its physical size is {16, 16, 1} as the block-compression algorithm can only operate on 4x4 texel blocks.

3.4.5. Synchronization

For each subresource of a physical resource, its set of internal usage flags is tracked on the Queue timeline.

This section will need to be revised to support multiple queues.

On the Queue timeline, there is an ordered sequence of usage scopes. Each item on the timeline is contained within exactly one scope. For the duration of each scope, the set of internal usage flags of any given subresource is constant. A subresource may transition to new usages at the boundaries between usage scopes.

This specification defines the following usage scopes:

  1. an individual command on a GPUCommandEncoder, such as GPUCommandEncoder.copyBufferToTexture.

  2. an individual command on a GPUComputePassEncoder, such as GPUProgrammablePassEncoder.setBindGroup.

  3. the whole GPURenderPassEncoder.

Resources that are used in state setting calls are always added as used resources in the containing usage scope. This means the following example resource usages are included in usage scope validation:

The usage scopes are validated at GPUCommandEncoder.finish time. The implementation performs the usage scope validation by composing the list of all internal usage flags of each subresource used in the usage scope. A GPUValidationError is generated in the current scope with an appropriate error message if that list is not a compatible usage list.

3.5. Core Internal Objects

3.5.1. Adapters

An adapter represents an implementation of WebGPU on the system. Each adapter identifies both an instance of a hardware accelerator (e.g. GPU or CPU) and an instance of a browser’s implementation of WebGPU on top of that accelerator.

If an adapter becomes unavailable, it becomes invalid. Once invalid, it never becomes valid again. Any devices on the adapter, and internal objects owned by those devices, also become invalid.

Note: An adapter may be a physical display adapter (GPU), but it could also be a software renderer. A returned adapter could refer to different physical adapters, or to different browser codepaths or system drivers on the same physical adapters. Applications can hold onto multiple adapters at once (via GPUAdapter) (even if some are invalid), and two of these could refer to different instances of the same physical configuration (e.g. if the GPU was reset or disconnected and reconnected).

An adapter has the following internal slots:

[[extensions]], of type list<GPUExtensionName>, readonly

The extensions which can be used to create devices on this adapter.

[[limits]], of type GPULimits, readonly

The best limits which can be used to create devices on this adapter.

Each adapter limit must be the same or better than its default value in GPULimits.

Adapters are exposed via GPUAdapter.

3.5.2. Devices

A device is the logical instantiation of an adapter, through which internal objects are created. It can be shared across multiple agents (e.g. dedicated workers).

A device is the exclusive owner of all internal objects created from it: when the device is lost, it and all objects created on it (directly, e.g. createTexture(), or indirectly, e.g. createView()) become invalid.

Define "ownership".

A device has the following internal slots:

[[adapter]], of type adapter, readonly

The adapter from which this device was created.

[[extensions]], of type list<GPUExtensionName>, readonly

The extensions which can be used on this device. No additional extensions can be used, even if the underlying adapter can support them.

[[limits]], of type GPULimits, readonly

The limits which can be used on this device. No better limits can be used, even if the underlying adapter can support them.

When a new device device is created from adapter adapter with GPUDeviceDescriptor descriptor:

Devices are exposed via GPUDevice.

3.6. Optional Capabilities

3.6.1. Limits

3.6.2. Extensions

4. Initialization

4.1. Examples

Need a robust example like the one in ErrorHandling.md, which handles all situations. Possibly also include a simple example with no handling.

A GPU object is available via navigator.gpu on the Window:

[Exposed=Window]
partial interface Navigator {
    [SameObject] readonly attribute GPU gpu;
};

... as well as on dedicated workers:

[Exposed=DedicatedWorker]
partial interface WorkerNavigator {
    [SameObject] readonly attribute GPU gpu;
};

4.3. GPU

GPU is the entry point to WebGPU.

[Exposed=(Window, DedicatedWorker)]
interface GPU {
    Promise<GPUAdapter?> requestAdapter(optional GPURequestAdapterOptions options = {});
};

GPU has the following methods:

requestAdapter(options)

Requests an adapter from the user agent. The user agent chooses whether to return an adapter, and, if so, chooses according to the provided options.

Called on: GPU this.

Arguments:

Arguments for the GPU.requestAdapter(options) method.
Parameter Type Nullable Optional Description
options GPURequestAdapterOptions Criteria used to select the adapter.

Returns: Promise<GPUAdapter?>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. If the user agent chooses to return an adapter:

      1. The user agent chooses an adapter adapter according to the rules in § 4.3.1 Adapter Selection and the criteria in options.

      2. promise resolves with a new GPUAdapter encapsulating adapter.

    2. Otherwise, promise resolves with null.

  3. Return promise.

4.3.1. Adapter Selection

GPURequestAdapterOptions provides hints to the user agent indicating what configuration is suitable for the application.

dictionary GPURequestAdapterOptions {
    GPUPowerPreference powerPreference;
};
enum GPUPowerPreference {
    "low-power",
    "high-performance"
};

GPURequestAdapterOptions has the following members:

powerPreference, of type GPUPowerPreference

Optionally provides a hint indicating what class of adapter should be selected from the system’s available adapters.

The value of this hint may influence which adapter is chosen, but it must not influence whether an adapter is returned or not.

Note: The primary utility of this hint is to influence which GPU is used in a multi-GPU system. For instance, some laptops have a low-power integrated GPU and a high-performance discrete GPU.

Note: Depending on the exact hardware configuration, such as battery status and attached displays or removable GPUs, the user agent may select different adapters given the same power preference. Typically, given the same hardware configuration and state and powerPreference, the user agent is likely to select the same adapter.

It must be one of the following values:

undefined (or not present)

Provides no hint to the user agent.

"low-power"

Indicates a request to prioritize power savings over performance.

Note: Generally, content should use this if it is unlikely to be constrained by drawing performance; for example, if it renders only one frame per second, draws only relatively simple geometry with simple shaders, or uses a small HTML canvas element. Developers are encouraged to use this value if their content allows, since it may significantly improve battery life on portable devices.

"high-performance"

Indicates a request to prioritize performance over power consumption.

Note: By choosing this value, developers should be aware that, for devices created on the resulting adapter, user agents are more likely to force device loss, in order to save power by switching to a lower-power adapter. Developers are encouraged to only specify this value if they believe it is absolutely necessary, since it may significantly decrease battery life on portable devices.

4.4. GPUAdapter

A GPUAdapter encapsulates an adapter, and describes its capabilities (extensions and limits).

To get a GPUAdapter, use requestAdapter().

interface GPUAdapter {
    readonly attribute DOMString name;
    readonly attribute FrozenArray<GPUExtensionName> extensions;
    //readonly attribute GPULimits limits; Don’t expose higher limits for now.

    Promise<GPUDevice?> requestDevice(optional GPUDeviceDescriptor descriptor = {});
};

GPUAdapter has the following attributes:

name, of type DOMString, readonly

A human-readable name identifying the adapter. The contents are implementation-defined.

extensions, of type FrozenArray<GPUExtensionName>, readonly

Accessor for this.[[adapter]].[[extensions]].

GPUAdapter has the following internal slots:

[[adapter]], of type adapter, readonly

The adapter to which this GPUAdapter refers.

GPUAdapter has the following methods:

requestDevice(descriptor)

Requests a device from the adapter.

Called on: GPUAdapter this.

Arguments:

Arguments for the GPUAdapter.requestDevice(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUDeviceDescriptor Description of the GPUDevice to request.

Returns: Promise<GPUDevice?>

  1. Let promise be a new promise.

  2. Issue the following steps to the Device timeline:

    1. If any of the following conditions are unsatisfied, reject promise with an OperationError and stop.

      where adapter is this.[[adapter]].

    2. If the user agent cannot fulfill the request, resolve promise to null and stop.

    3. Resolve promise to a new GPUDevice object encapsulating a new device with the capabilities described by descriptor.

  3. Return promise.

4.4.1. GPUDeviceDescriptor

GPUDeviceDescriptor describes a device request.

dictionary GPUDeviceDescriptor : GPUObjectDescriptorBase {
    sequence<GPUExtensionName> extensions = [];
    GPULimits limits = {};
};

GPUDeviceDescriptor has the following members:

extensions, of type sequence<GPUExtensionName>, defaulting to []

The set of GPUExtensionName values in this sequence defines the exact set of extensions that must be enabled on the device.

limits, of type GPULimits, defaulting to {}

Defines the exact limits that must be enabled on the device.

4.4.1.1. GPUExtensionName

Each GPUExtensionName identifies a set of functionality which, if available, allows additional usages of WebGPU that would have otherwise been invalid.

enum GPUExtensionName {
    "depth-clamping",
    "depth24unorm-stencil8",
    "depth32float-stencil8",
    "pipeline-statistics-query",
    "texture-compression-bc",
    "timestamp-query",
};
"texture-compression-bc"

Write a spec section for this, and link to it.

"depth24unorm-stencil8"

Allows for explicit creation of textures of format "depth24unorm-stencil8".

"depth32float-stencil8"

Allows for explicit creation of textures of format "depth32float-stencil8".

4.4.1.2. GPULimits

GPULimits describes various limits in the usage of WebGPU on a device.

One limit value may be better than another. For each limit, "better" is defined.

Note: Setting "better" limits may not necessarily be desirable. While they enable strictly more programs to be valid, they may have a performance impact. Because of this, and to improve portability across devices and implementations, applications should generally request the "worst" limits that work for their content.

dictionary GPULimits {
    GPUSize32 maxBindGroups = 4;
    GPUSize32 maxDynamicUniformBuffersPerPipelineLayout = 8;
    GPUSize32 maxDynamicStorageBuffersPerPipelineLayout = 4;
    GPUSize32 maxSampledTexturesPerShaderStage = 16;
    GPUSize32 maxSamplersPerShaderStage = 16;
    GPUSize32 maxStorageBuffersPerShaderStage = 4;
    GPUSize32 maxStorageTexturesPerShaderStage = 4;
    GPUSize32 maxUniformBuffersPerShaderStage = 12;
    GPUSize32 maxUniformBufferBindingSize = 16384;
};
maxBindGroups, of type GPUSize32, defaulting to 4

The maximum number of GPUBindGroupLayouts allowed in bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxDynamicUniformBuffersPerPipelineLayout, of type GPUSize32, defaulting to 8

The maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxDynamicStorageBuffersPerPipelineLayout, of type GPUSize32, defaulting to 4

The maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxSampledTexturesPerShaderStage, of type GPUSize32, defaulting to 16

For each possible GPUShaderStage stage, the maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxSamplersPerShaderStage, of type GPUSize32, defaulting to 16

For each possible GPUShaderStage stage, the maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxStorageBuffersPerShaderStage, of type GPUSize32, defaulting to 4

For each possible GPUShaderStage stage, the maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxStorageTexturesPerShaderStage, of type GPUSize32, defaulting to 4

For each possible GPUShaderStage stage, the maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxUniformBuffersPerShaderStage, of type GPUSize32, defaulting to 12

For each possible GPUShaderStage stage, the maximum number of entries for which:

across all bindGroupLayouts when creating a GPUPipelineLayout.

Higher is better.

maxUniformBufferBindingSize, of type GPUSize32, defaulting to 16384

The maximum GPUBufferBinding.size for bindings of type "uniform-buffer".

Higher is better.

4.5. GPUDevice

A GPUDevice encapsulates a device and exposes the functionality of that device.

GPUDevice is the top-level interface through which WebGPU interfaces are created.

To get a GPUDevice, use requestDevice().

[Exposed=(Window, DedicatedWorker), Serializable]
interface GPUDevice : EventTarget {
    [SameObject] readonly attribute GPUAdapter adapter;
    readonly attribute FrozenArray<GPUExtensionName> extensions;
    readonly attribute object limits;

    [SameObject] readonly attribute GPUQueue defaultQueue;

    GPUBuffer createBuffer(GPUBufferDescriptor descriptor);
    GPUTexture createTexture(GPUTextureDescriptor descriptor);
    GPUSampler createSampler(optional GPUSamplerDescriptor descriptor = {});

    GPUBindGroupLayout createBindGroupLayout(GPUBindGroupLayoutDescriptor descriptor);
    GPUPipelineLayout createPipelineLayout(GPUPipelineLayoutDescriptor descriptor);
    GPUBindGroup createBindGroup(GPUBindGroupDescriptor descriptor);

    GPUShaderModule createShaderModule(GPUShaderModuleDescriptor descriptor);
    GPUComputePipeline createComputePipeline(GPUComputePipelineDescriptor descriptor);
    GPURenderPipeline createRenderPipeline(GPURenderPipelineDescriptor descriptor);
    Promise<GPUComputePipeline> createReadyComputePipeline(GPUComputePipelineDescriptor descriptor);
    Promise<GPURenderPipeline> createReadyRenderPipeline(GPURenderPipelineDescriptor descriptor);

    GPUCommandEncoder createCommandEncoder(optional GPUCommandEncoderDescriptor descriptor = {});
    GPURenderBundleEncoder createRenderBundleEncoder(GPURenderBundleEncoderDescriptor descriptor);

    GPUQuerySet createQuerySet(GPUQuerySetDescriptor descriptor);
};
GPUDevice includes GPUObjectBase;

GPUDevice has the following attributes:

adapter, of type GPUAdapter, readonly

The GPUAdapter from which this device was created.

extensions, of type FrozenArray<GPUExtensionName>, readonly

A sequence containing the GPUExtensionNames of the extensions supported by the device (i.e. the ones with which it was created).

limits, of type object, readonly

A GPULimits object exposing the limits supported by the device (i.e. the ones with which it was created).

defaultQueue, of type GPUQueue, readonly

The default GPUQueue for this device.

GPUDevice has the following internal slots:

[[device]], of type device, readonly

The device that this GPUDevice refers to.

GPUDevice has the methods listed in its WebIDL definition above, which are defined elsewhere in this document.

GPUDevice objects are serializable objects.

The steps to serialize a GPUDevice object, given value, serialized, and forStorage, are:
  1. If forStorage is true, throw a "DataCloneError".

  2. Set serialized.device to the value of value.[[device]].

The steps to deserialize a GPUDevice object, given serialized and value, are:
  1. Set value.[[device]] to serialized.device.

5. Buffers

5.1. GPUBuffer

define buffer (internal object)

A GPUBuffer represents a block of memory that can be used in GPU operations. Data is stored in linear layout, meaning that each byte of the allocation can be addressed by its offset from the start of the GPUBuffer, subject to alignment restrictions depending on the operation. Some GPUBuffers can be mapped which makes the block of memory accessible via an ArrayBuffer called its mapping.

GPUBuffers are created via GPUDevice.createBuffer(descriptor) that returns a new buffer in the mapped or unmapped state.

[Serializable]
interface GPUBuffer {
    Promise<undefined> mapAsync(GPUMapModeFlags mode, optional GPUSize64 offset = 0, optional GPUSize64 size);
    ArrayBuffer getMappedRange(optional GPUSize64 offset = 0, optional GPUSize64 size);
    undefined unmap();

    undefined destroy();
};
GPUBuffer includes GPUObjectBase;

GPUBuffer has the following internal slots:

[[size]] of type GPUSize64.

The length of the GPUBuffer allocation in bytes.

[[usage]] of type GPUBufferUsageFlags.

The allowed usages for this GPUBuffer.

[[state]] of type buffer state.

The current state of the GPUBuffer.

[[mapping]] of type ArrayBuffer or Promise or null.

The mapping for this GPUBuffer. The ArrayBuffer isn’t directly accessible and is instead accessed through views into it, called the mapped ranges, that are stored in [[mapped_ranges]]

Specify [[mapping]] in term of DataBlock similarly to AllocateArrayBuffer? <https://github.com/gpuweb/gpuweb/issues/605>

[[mapping_range]] of type list<Number> or null.

The range of this GPUBuffer that is mapped.

[[mapped_ranges]] of type list<ArrayBuffer> or null.

The ArrayBuffers returned via getMappedRange to the application. They are tracked so they can be detached when unmap is called.

[[map_mode]] of type GPUMapModeFlags.

The GPUMapModeFlags of the last call to mapAsync() (if any).

[[usage]] is differently named from [[textureUsage]]. We should make it consistent.

Each GPUBuffer has a current buffer state on the Content timeline which is one of the following:

Note: [[size]] and [[usage]] are immutable once the GPUBuffer has been created.

Note: GPUBuffer has a state machine with the following states. ([[mapping]], [[mapping_range]], and [[mapped_ranges]] are null when not specified.)

GPUBuffer is Serializable. It is a reference to an internal buffer object, and Serializable means that the reference can be copied between realms (threads/workers), allowing multiple realms to access it concurrently. Since GPUBuffer has internal state (mapped, destroyed), that state is internally-synchronized - these state changes occur atomically across realms.

5.2. Buffer Creation

5.2.1. GPUBufferDescriptor

This specifies the options to use in creating a GPUBuffer.

dictionary GPUBufferDescriptor : GPUObjectDescriptorBase {
    required GPUSize64 size;
    required GPUBufferUsageFlags usage;
    boolean mappedAtCreation = false;
};
validating GPUBufferDescriptor(device, descriptor)
  1. If device is lost return false.

  2. If any of the bits of descriptor’s usage aren’t present in this device’s [[allowed buffer usages]] return false.

  3. If both the MAP_READ and MAP_WRITE bits of descriptor’s usage attribute are set, return false.

  4. Return true.

5.3. Buffer Usage

typedef [EnforceRange] unsigned long GPUBufferUsageFlags;
interface GPUBufferUsage {
    const GPUFlagsConstant MAP_READ      = 0x0001;
    const GPUFlagsConstant MAP_WRITE     = 0x0002;
    const GPUFlagsConstant COPY_SRC      = 0x0004;
    const GPUFlagsConstant COPY_DST      = 0x0008;
    const GPUFlagsConstant INDEX         = 0x0010;
    const GPUFlagsConstant VERTEX        = 0x0020;
    const GPUFlagsConstant UNIFORM       = 0x0040;
    const GPUFlagsConstant STORAGE       = 0x0080;
    const GPUFlagsConstant INDIRECT      = 0x0100;
    const GPUFlagsConstant QUERY_RESOLVE = 0x0200;
};
createBuffer(descriptor)

Creates a GPUBuffer.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBuffer(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBufferDescriptor Description of the GPUBuffer to create.

Returns: GPUBuffer

  1. If any of the following conditions are unsatisfied, return an error buffer and stop.

    Explain that the resulting error buffer can still be mapped at creation. <https://github.com/gpuweb/gpuweb/issues/605>

    Explain what are a GPUDevice's [[allowed buffer usages]]. <https://github.com/gpuweb/gpuweb/issues/605>

  2. Let b be a new GPUBuffer object.

  3. Set b.[[size]] to descriptor.size.

  4. Set b.[[usage]] to descriptor.usage.

  5. If descriptor.mappedAtCreation is true:

    1. Set b.[[mapping]] to a new ArrayBuffer of size b.[[size]].

    2. Set b.[[mapping_range]] to [0, descriptor.size].

    3. Set b.[[mapped_ranges]] to [].

    4. Set b.[[state]] to mapped at creation.

    Else:

    1. Set b.[[mapping]] to null.

    2. Set b.[[mapping_range]] to null.

    3. Set b.[[mapped_ranges]] to null.

    4. Set b.[[state]] to unmapped.

  6. Set each byte of b’s allocation to zero.

  7. Return b.

Note: it is valid to set mappedAtCreation to true without MAP_READ or MAP_WRITE in usage. This can be used to set the buffer’s initial data.

5.4. Buffer Destruction

An application that no longer requires a GPUBuffer can choose to lose access to it before garbage collection by calling destroy().

Note: This allows the user agent to reclaim the GPU memory associated with the GPUBuffer once all previously submitted operations using it are complete.

destroy()

Destroys the GPUBuffer.

Called on: GPUBuffer this.

Returns: undefined

  1. If the this.[[state]] is mapped or mapped at creation:

    1. Run the steps to unmap this.

  2. Set this.[[state]] to destroyed.

Handle error buffers once we have a description of the error monad.

5.5. Buffer Mapping

An application can request to map a GPUBuffer so that they can access its content via ArrayBuffers that represent part of the GPUBuffer's allocations. Mapping a GPUBuffer is requested asynchronously with mapAsync() so that the user agent can ensure the GPU finished using the GPUBuffer before the application can access its content. Once the GPUBuffer is mapped the application can synchronously ask for access to ranges of its content with getMappedRange. A mapped GPUBuffer cannot be used by the GPU and must be unmapped using unmap before work using it can be submitted to the Queue timeline.

Add client-side validation that a mapped buffer can only be unmapped and destroyed on the worker on which it was mapped. Likewise getMappedRange can only be called on that worker. <https://github.com/gpuweb/gpuweb/issues/605>

typedef [EnforceRange] unsigned long GPUMapModeFlags;
interface GPUMapMode {
    const GPUFlagsConstant READ  = 0x0001;
    const GPUFlagsConstant WRITE = 0x0002;
};
mapAsync(mode, offset, size)

Maps the given range of the GPUBuffer and resolves the returned Promise when the GPUBuffer's content is ready to be accessed with getMappedRange().

Called on: GPUBuffer this.

Arguments:

Arguments for the GPUBuffer.mapAsync(mode, offset, size) method.
Parameter Type Nullable Optional Description
mode GPUMapModeFlags Whether the buffer should be mapped for reading or writing.
offset GPUSize64 Offset in bytes into the buffer to the start of the range to map.
size GPUSize64 Size in bytes of the range to map.

Returns: Promise<undefined>

Handle error buffers once we have a description of the error monad. <https://github.com/gpuweb/gpuweb/issues/605>

  1. If size is unspecified:

    1. If offset > this.[[size]], reject with an OperationError and stop.

    2. Let rangeSize be this.[[size]] - offset.

    Otherwise, let rangeSize be size.

  2. If any of the following conditions are unsatisfied:

    Do we validate that mode contains only valid flags?

    Then:

    1. Record a validation error on the current scope.

    2. Return a promise rejected with an AbortError on the Device timeline.

  3. Let p be a new Promise.

  4. Set this.[[mapping]] to p.

  5. Set this.[[state]] to mapping pending.

  6. Set this.[[map_mode]] to mode.

  7. Enqueue an operation on the default queue’s Queue timeline that will execute the following:

    1. If this.[[state]] is mapping pending:

      1. Let m be a new ArrayBuffer of size rangeSize.

      2. Set the content of m to the content of this’s allocation starting at offset offset and for rangeSize bytes.

      3. Set this.[[mapping]] to m.

      4. Set this.[[state]] to mapped.

      5. Set this.[[mapping_range]] to [offset, offset + rangeSize].

      6. Set this.[[mapped_ranges]] to [].

    2. Resolve p.

  8. Return p.

getMappedRange(offset, size)

Returns a ArrayBuffer with the contents of the GPUBuffer in the given mapped range.

Called on: GPUBuffer this.

Arguments:

Arguments for the GPUBuffer.getMappedRange(offset, size) method.
Parameter Type Nullable Optional Description
offset GPUSize64 Offset in bytes into the buffer to return buffer contents from.
size GPUSize64 Size in bytes of the ArrayBuffer to return.

Returns: ArrayBuffer

  1. If size is unspecified:

    1. If offset > this.[[size]], throw an OperationError and stop.

    2. Let rangeSize be this.[[size]] - offset.

    Else:

    1. Let rangeSize be size.

  2. If any of the following conditions are unsatisfied, throw an OperationError and stop.

    Note: It is always valid to get mapped ranges of a GPUBuffer that is mapped at creation, even if it is invalid, because the Content timeline might not know it is invalid.

    Consider aligning mapAsync offset to 8 to match this.

  3. Let m be a new ArrayBuffer of size rangeSize pointing at the content of this.[[mapping]] at offset offset - this.[[mapping_range]][0].

  4. Append m to this.[[mapped_ranges]].

  5. Return m.

unmap()

Unmaps the mapped range of the GPUBuffer and makes it’s contents available for use by the GPU again.

Called on: GPUBuffer this.

Returns: undefined

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    Note: It is valid to unmap an error GPUBuffer that is mapped at creation because the Content timeline might not know it is an error GPUBuffer.

  2. If this.[[state]] is mapping pending:

    1. Reject [[mapping]] with an OperationError.

    2. Set this.[[mapping]] to null.

  3. If this.[[state]] is mapped or mapped at creation:

    1. If one of the two following conditions holds:

      Then:

      1. Enqueue an operation on the default queue’s Queue timeline that updates the this.[[mapping_range]] of this’s allocation to the content of this.[[mapping]].

    2. Detach each ArrayBuffer in this.[[mapped_ranges]] from its content.

    3. Set this.[[mapping]] to null.

    4. Set this.[[mapping_range]] to null.

    5. Set this.[[mapped_ranges]] to null.

  4. Set this.[[state]] to unmapped.

Note: When a MAP_READ buffer (not currently mapped at creation) is unmapped, any local modifications done by the application to the mapped ranges ArrayBuffer are discarded and will not affect the content of follow-up mappings.

6. Textures and Texture Views

define texture (internal object)

define mipmap level, array layer, aspect, slice (concepts)

6.1. GPUTexture

[Serializable]
interface GPUTexture {
    GPUTextureView createView(optional GPUTextureViewDescriptor descriptor = {});

    undefined destroy();
};
GPUTexture includes GPUObjectBase;

GPUTexture has the following internal slots:

[[textureSize]] of type GPUExtent3D.

The size of the GPUTexture in texels in mipmap level 0.

[[mipLevelCount]] of type GPUIntegerCoordinate.

The total number of the mipmap levels of the GPUTexture.

[[sampleCount]] of type GPUSize32.

The number of samples in each texel of the GPUTexture.

[[dimension]] of type GPUTextureDimension.

The dimension of the GPUTexture.

[[format]] of type GPUTextureFormat.

The format of the GPUTexture.

[[textureUsage]] of type GPUTextureUsageFlags.

The allowed usages for this GPUTexture.

6.1.1. Texture Creation

dictionary GPUTextureDescriptor : GPUObjectDescriptorBase {
    required GPUExtent3D size;
    GPUIntegerCoordinate mipLevelCount = 1;
    GPUSize32 sampleCount = 1;
    GPUTextureDimension dimension = "2d";
    required GPUTextureFormat format;
    required GPUTextureUsageFlags usage;
};
enum GPUTextureDimension {
    "1d",
    "2d",
    "3d"
};
typedef [EnforceRange] unsigned long GPUTextureUsageFlags;
interface GPUTextureUsage {
    const GPUFlagsConstant COPY_SRC          = 0x01;
    const GPUFlagsConstant COPY_DST          = 0x02;
    const GPUFlagsConstant SAMPLED           = 0x04;
    const GPUFlagsConstant STORAGE           = 0x08;
    const GPUFlagsConstant OUTPUT_ATTACHMENT = 0x10;
};
createTexture(descriptor)

Creates a GPUTexture.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createTexture(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUTextureDescriptor Description of the GPUTexture to create.

Returns: GPUTexture

Describe createTexture() algorithm steps.

6.1.2. Texture Destruction

An application that no longer requires a GPUTexture can choose to lose access to it before garbage collection by calling destroy().

Note: This allows the user agent to reclaim the GPU memory associated with the GPUTexture once all previously submitted operations using it are complete.

destroy()

Destroys the GPUTexture.

Called on: GPUTexture this.

Returns: undefined

Describe destroy() algorithm steps.

6.2. GPUTextureView

interface GPUTextureView {
};
GPUTextureView includes GPUObjectBase;

GPUTextureView has the following internal slots:

[[texture]]

The GPUTexture into which this is a view.

[[descriptor]]

The GPUTextureViewDescriptor describing this texture view.

All optional fields of GPUTextureViewDescriptor are defined.

6.2.1. Texture View Creation

dictionary GPUTextureViewDescriptor : GPUObjectDescriptorBase {
    GPUTextureFormat format;
    GPUTextureViewDimension dimension;
    GPUTextureAspect aspect = "all";
    GPUIntegerCoordinate baseMipLevel = 0;
    GPUIntegerCoordinate mipLevelCount;
    GPUIntegerCoordinate baseArrayLayer = 0;
    GPUIntegerCoordinate arrayLayerCount;
};

Make this a standalone algorithm used in the createView algorithm.

The references to GPUTextureDescriptor here should actually refer to internal slots of a texture internal object once we have one.

enum GPUTextureViewDimension {
    "1d",
    "2d",
    "2d-array",
    "cube",
    "cube-array",
    "3d"
};
enum GPUTextureAspect {
    "all",
    "stencil-only",
    "depth-only"
};
createView(descriptor)

Creates a GPUTextureView.

Called on: GPUTexture this.

Arguments:

Arguments for the GPUTexture.createView(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUTextureViewDescriptor Description of the GPUTextureView to create.

Returns: view, of type GPUTextureView.

write definition. this descriptor view

6.3. Texture Formats

The name of the format specifies the order of components, bits per component, and data type for the component.

If the format has the -srgb suffix, then sRGB conversions from gamma to linear and vice versa are applied during the reading and writing of color values in the shader. Compressed texture formats are provided by extensions. Their naming should follow the convention here, with the texture name as a prefix. e.g. etc2-rgba8unorm.

The texel block is a single addressable element of the textures in pixel-based GPUTextureFormats, and a single compressed block of the textures in block-based compressed GPUTextureFormats.

The texel block width and texel block height specifies the dimension of one texel block.

The texel block size of a GPUTextureFormat is the number of bytes to store one texel block. The texel block size of each GPUTextureFormat is constant except for "stencil8", "depth24plus", and "depth24plus-stencil8".

enum GPUTextureFormat {
    // 8-bit formats
    "r8unorm",
    "r8snorm",
    "r8uint",
    "r8sint",

    // 16-bit formats
    "r16uint",
    "r16sint",
    "r16float",
    "rg8unorm",
    "rg8snorm",
    "rg8uint",
    "rg8sint",

    // 32-bit formats
    "r32uint",
    "r32sint",
    "r32float",
    "rg16uint",
    "rg16sint",
    "rg16float",
    "rgba8unorm",
    "rgba8unorm-srgb",
    "rgba8snorm",
    "rgba8uint",
    "rgba8sint",
    "bgra8unorm",
    "bgra8unorm-srgb",
    // Packed 32-bit formats
    "rgb9e5ufloat",
    "rgb10a2unorm",
    "rg11b10ufloat",

    // 64-bit formats
    "rg32uint",
    "rg32sint",
    "rg32float",
    "rgba16uint",
    "rgba16sint",
    "rgba16float",

    // 128-bit formats
    "rgba32uint",
    "rgba32sint",
    "rgba32float",

    // Depth and stencil formats
    "stencil8",
    "depth16unorm",
    "depth24plus",
    "depth24plus-stencil8",
    "depth32float",

    // BC compressed formats usable if "texture-compression-bc" is both
    // supported by the device/user agent and enabled in requestDevice.
    "bc1-rgba-unorm",
    "bc1-rgba-unorm-srgb",
    "bc2-rgba-unorm",
    "bc2-rgba-unorm-srgb",
    "bc3-rgba-unorm",
    "bc3-rgba-unorm-srgb",
    "bc4-r-unorm",
    "bc4-r-snorm",
    "bc5-rg-unorm",
    "bc5-rg-snorm",
    "bc6h-rgb-ufloat",
    "bc6h-rgb-float",
    "bc7-rgba-unorm",
    "bc7-rgba-unorm-srgb",

    // "depth24unorm-stencil8" extension
    "depth24unorm-stencil8",

    // "depth32float-stencil8" extension
    "depth32float-stencil8",
};

The depth aspect of the "depth24plus") and "depth24plus-stencil8") formats may be implemented as either a 24-bit unsigned normalized value ("depth24unorm") or a 32-bit IEEE 754 floating point value ("depth32float").

add something on GPULimits that gives an estimate of the bytes per texel of "stencil8"

The stencil8) format may be implemented as either a real "stencil8", or "depth24stencil8", where the depth aspect is hidden and inaccessible.

Note: While the precision of depth32float is strictly higher than the precision of depth24unorm for all values in the representable range (0.0 to 1.0), note that the set of representable values is not exactly the same: for depth24unorm, 1 ULP has a constant value of 1 / (224 − 1); for depth32float, 1 ULP has a variable value no greater than 1 / (224).

"rgb9e5ufloat" cannot be used as a color attachment.

enum GPUTextureComponentType {
    "float",
    "sint",
    "uint",
    // Texture is used with comparison sampling only.
    "depth-comparison"
};

7. Samplers

7.1. GPUSampler

A GPUSampler encodes transformations and filtering information that can be used in a shader to interpret texture resource data.

GPUSamplers are created via GPUDevice.createSampler(optional descriptor) that returns a new sampler object.

interface GPUSampler {
};
GPUSampler includes GPUObjectBase;

GPUSampler has the following internal slots:

[[descriptor]], of type GPUSamplerDescriptor, readonly

The GPUSamplerDescriptor with which the GPUSampler was created.

[[compareEnable]] of type boolean.

Whether the GPUSampler is used as a comparison sampler.

7.2. Sampler Creation

7.2.1. GPUSamplerDescriptor

A GPUSamplerDescriptor specifies the options to use to create a GPUSampler.

dictionary GPUSamplerDescriptor : GPUObjectDescriptorBase {
    GPUAddressMode addressModeU = "clamp-to-edge";
    GPUAddressMode addressModeV = "clamp-to-edge";
    GPUAddressMode addressModeW = "clamp-to-edge";
    GPUFilterMode magFilter = "nearest";
    GPUFilterMode minFilter = "nearest";
    GPUFilterMode mipmapFilter = "nearest";
    float lodMinClamp = 0;
    float lodMaxClamp = 0xffffffff; // TODO: What should this be? Was Number.MAX_VALUE.
    GPUCompareFunction compare;
    unsigned short maxAnisotropy = 1;
};

explain how LOD is calculated and if there are differences here between platforms. Issue: explain what anisotropic sampling is

GPUAddressMode describes the behavior of the sampler if the sample footprint extends beyond the bounds of the sampled texture.

Describe a "sample footprint" in greater detail.

enum GPUAddressMode {
    "clamp-to-edge",
    "repeat",
    "mirror-repeat"
};
"clamp-to-edge"

Texture coordinates are clamped between 0.0 and 1.0, inclusive.

"repeat"

Texture coordinates wrap to the other side of the texture.

"mirror-repeat"

Texture coordinates wrap to the other side of the texture, but the texture is flipped when the integer part of the coordinate is odd.

GPUFilterMode describes the behavior of the sampler if the sample footprint does not exactly match one texel.

enum GPUFilterMode {
    "nearest",
    "linear"
};
"nearest"

Return the value of the texel nearest to the texture coordinates.

"linear"

Select two texels in each dimension and return a linear interpolation between their values.

GPUCompareFunction specifies the behavior of a comparison sampler. If a comparison sampler is used in a shader, an input value is compared to the sampled texture value, and the result of this comparison test (0.0f for pass, or 1.0f for fail) is used in the filtering operation.

describe how filtering interacts with comparison sampling.

enum GPUCompareFunction {
    "never",
    "less",
    "equal",
    "less-equal",
    "greater",
    "not-equal",
    "greater-equal",
    "always"
};
"never"

Comparison tests never pass.

"less"

A provided value passes the comparison test if it is less than the sampled value.

"equal"

A provided value passes the comparison test if it is equal to the sampled value.

"less-equal"

A provided value passes the comparison test if it is less than or equal to the sampled value.

"greater"

A provided value passes the comparison test if it is greater than the sampled value.

"not-equal"

A provided value passes the comparison test if it is not equal to the sampled value.

"greater-equal"

A provided value passes the comparison test if it is greater than or equal to the sampled value.

"always"

Comparison tests always pass.

validating GPUSamplerDescriptor(device, descriptor) Arguments:

Returns: boolean

Return true if and only if all of the following conditions are satisfied:

createSampler(descriptor)

Creates a GPUBindGroupLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createSampler(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUSamplerDescriptor Description of the GPUSampler to create.

Returns: GPUSampler

  1. Let s be a new GPUSampler object.

  2. Set s.[[descriptor]] to descriptor.

  3. Set s.[[compareEnable]] to false if the compare attribute of s.[[descriptor]] is null or undefined. Otherwise, set it to true.

  4. Return s.

Valid Usage

8. Resource Binding

8.1. GPUBindGroupLayout

A GPUBindGroupLayout defines the interface between a set of resources bound in a GPUBindGroup and their accessibility in shader stages.

[Serializable]
interface GPUBindGroupLayout {
};
GPUBindGroupLayout includes GPUObjectBase;

8.1.1. Creation

A GPUBindGroupLayout is created via GPUDevice.createBindGroupLayout().

dictionary GPUBindGroupLayoutDescriptor : GPUObjectDescriptorBase {
    required sequence<GPUBindGroupLayoutEntry> entries;
};

A GPUBindGroupLayoutEntry describes a single shader resource binding to be included in a GPUBindGroupLayout.

dictionary GPUBindGroupLayoutEntry {
    required GPUIndex32 binding;
    required GPUShaderStageFlags visibility;
    required GPUBindingType type;

    // Used for uniform buffer and storage buffer bindings. Must be undefined for other binding types.
    boolean hasDynamicOffset;

    // Used for uniform buffer and storage buffer bindings. Must be undefined for other binding types.
    GPUSize64 minBufferBindingSize;

    // Used for sampled texture and storage texture bindings. Must be undefined for other binding types.
    GPUTextureViewDimension viewDimension;

    // Used for sampled texture bindings. Must be undefined for other binding types.
    GPUTextureComponentType textureComponentType;

    // Used for storage texture bindings. Must be undefined for other binding types.
    GPUTextureFormat storageTextureFormat;
};

consider making textureComponentType and storageTextureFormat truly optional.

binding, of type GPUIndex32

A unique identifier for a resource binding within a GPUBindGroupLayoutEntry, a corresponding GPUBindGroupEntry, and the GPUShaderModules.

visibility, of type GPUShaderStageFlags

A bitset of the members of GPUShaderStage. Each set bit indicates that a GPUBindGroupLayoutEntry's resource will be accessible from the associated shader stage.

type, of type GPUBindingType

The type of the binding. The value of this member influences the interpretation of other members.

Note: This member is used to determine compatibility between a GPUPipelineLayout and a GPUShaderModule.

hasDynamicOffset, of type boolean

If the binding resource type for type is GPUBufferBinding:

  • This indicates whether a binding requires a dynamic offset.

  • If undefined, it defaults to false.

Otherwise, it must be undefined.

minBufferBindingSize, of type GPUSize64

If the binding resource type for type is GPUBufferBinding:

  • This may be used to indicate the minimum buffer binding size.

  • If undefined, it defaults to 0.

Otherwise, it must be undefined.

viewDimension, of type GPUTextureViewDimension

If the binding resource type for type is GPUTextureView:

  • This is the required dimension of a texture view bound to this binding.

  • If undefined, it defaults to "2d".

Otherwise, it must be undefined.

textureComponentType, of type GPUTextureComponentType

If the type is "sampled-texture":

  • This is the required component type of the format of a texture view bound to this binding.

  • If undefined, it defaults to "float".

Otherwise, it must be undefined.

storageTextureFormat, of type GPUTextureFormat

If the type is "readonly-storage-texture" or "writeonly-storage-texture":

  • This is the required format of a texture view bound to this binding.

Otherwise, it must be undefined.

Note: viewDimension enables Metal-based WebGPU implementations to back the respective bind groups with MTLArgumentBuffer objects that are more efficient to bind at run-time.

typedef [EnforceRange] unsigned long GPUShaderStageFlags;
interface GPUShaderStage {
    const GPUFlagsConstant VERTEX   = 0x1;
    const GPUFlagsConstant FRAGMENT = 0x2;
    const GPUFlagsConstant COMPUTE  = 0x4;
};
enum GPUBindingType {
    "uniform-buffer",
    "storage-buffer",
    "readonly-storage-buffer",
    "sampler",
    "comparison-sampler",
    "sampled-texture",
    "multisampled-texture",
    "readonly-storage-texture",
    "writeonly-storage-texture"
};

Each GPUBindingType has an associated GPUBindingResource type and internal usage, given by this table:

GPUBindingType Binding resource type Binding usage
"uniform-buffer" GPUBufferBinding constant
"storage-buffer" GPUBufferBinding storage
"readonly-storage-buffer" GPUBufferBinding storage-read
"sampler" GPUSampler constant
"comparison-sampler" GPUSampler constant
"sampled-texture" GPUTextureView constant
"multisampled-texture" GPUTextureView constant
"readonly-storage-texture" GPUTextureView storage-read
"writeonly-storage-texture" GPUTextureView storage-write

A GPUBindGroupLayout object has the following internal slots:

[[entryMap]] of type ordered map<GPUSize32, GPUBindGroupLayoutEntry>.

The map of binding indices pointing to the GPUBindGroupLayoutEntrys, which this GPUBindGroupLayout describes.

[[dynamicOffsetCount]] of type GPUSize32.

The number of buffer bindings with dynamic offsets in this GPUBindGroupLayout.

createBindGroupLayout(descriptor)

Creates a GPUBindGroupLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBindGroupLayout(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBindGroupLayoutDescriptor Description of the GPUBindGroupLayout to create.

Returns: GPUBindGroupLayout

  1. Let layout be a new valid GPUBindGroupLayout object.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make layout invalid and return layout.

    2. Set layout.[[dynamicOffsetCount]] to the number of entries in descriptor where hasDynamicOffset is true.

    3. For each GPUBindGroupLayoutEntry bindingDescriptor in descriptor.entries:

      1. Insert bindingDescriptor into layout.[[entryMap]] with the key of bindingDescriptor.binding.

      Add a step to bake the default values (e.g. viewDimension to "2d") into the bindingDescriptor.

  3. Return layout.

8.1.2. Compatibility

Two GPUBindGroupLayout objects a and b are considered group-equivalent if and only if, for any binding number binding, one of the following conditions is satisfied:

If bind groups layouts are group-equivalent they can be interchangeably used in all contents.

8.2. GPUBindGroup

A GPUBindGroup defines a set of resources to be bound together in a group and how the resources are used in shader stages.

interface GPUBindGroup {
};
GPUBindGroup includes GPUObjectBase;

8.2.1. Bind Group Creation

A GPUBindGroup is created via GPUDevice.createBindGroup().

dictionary GPUBindGroupDescriptor : GPUObjectDescriptorBase {
    required GPUBindGroupLayout layout;
    required sequence<GPUBindGroupEntry> entries;
};

A GPUBindGroupEntry describes a single resource to be bound in a GPUBindGroup.

typedef (GPUSampler or GPUTextureView or GPUBufferBinding) GPUBindingResource;

dictionary GPUBindGroupEntry {
    required GPUIndex32 binding;
    required GPUBindingResource resource;
};
dictionary GPUBufferBinding {
    required GPUBuffer buffer;
    GPUSize64 offset = 0;
    GPUSize64 size;
};

A GPUBindGroup object has the following internal slots:

[[layout]] of type GPUBindGroupLayout.

The GPUBindGroupLayout associated with this GPUBindGroup.

[[entries]] of type sequence<GPUBindGroupEntry>.

The set of GPUBindGroupEntrys this GPUBindGroup describes.

[[usedResources]] of type ordered map<subresource, list<internal usage>>.

The set of buffer and texture subresources used by this bind group, associated with lists of the internal usage flags.

createBindGroup(descriptor)

Creates a GPUBindGroup.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createBindGroup(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUBindGroupDescriptor Description of the GPUBindGroup to create.

Returns: GPUBindGroup

  1. Let bindGroup be a new valid GPUBindGroup object.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      For each GPUBindGroupEntry bindingDescriptor in descriptor.entries:

      define the association between texture formats and component types

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make bindGroup invalid and return bindGroup.

    2. Let bindGroup.[[layout]] = descriptor.layout.

    3. Let bindGroup.[[entries]] = descriptor.entries.

    4. Let bindGroup.[[usedResources]] = {}.

    5. For each GPUBindGroupEntry bindingDescriptor in descriptor.entries:

      1. Let internalUsage be the binding usage for layoutBinding.type.

      2. Each subresource seen by resource is added to [[usedResources]] as internalUsage.

  3. Return bindGroup.

define the "effective buffer binding size" separately.

8.3. GPUPipelineLayout

A GPUPipelineLayout defines the mapping between resources of all GPUBindGroup objects set up during command encoding in setBindGroup, and the shaders of the pipeline set by GPURenderEncoderBase.setPipeline or GPUComputePassEncoder.setPipeline.

The full binding address of a resource can be defined as a trio of:

  1. shader stage mask, to which the resource is visible

  2. bind group index

  3. binding number

The components of this address can also be seen as the binding space of a pipeline. A GPUBindGroup (with the corresponding GPUBindGroupLayout) covers that space for a fixed bind group index. The contained bindings need to be a superset of the resources used by the shader at this bind group index.

[Serializable]
interface GPUPipelineLayout {
};
GPUPipelineLayout includes GPUObjectBase;

GPUPipelineLayout has the following internal slots:

[[bindGroupLayouts]] of type list<GPUBindGroupLayout>.

The GPUBindGroupLayout objects provided at creation in GPUPipelineLayoutDescriptor.bindGroupLayouts.

Note: using the same GPUPipelineLayout for many GPURenderPipeline or GPUComputePipeline pipelines guarantees that the user agent doesn’t need to rebind any resources internally when there is a switch between these pipelines.

GPUComputePipeline object X was created with GPUPipelineLayout.bindGroupLayouts A, B, C. GPUComputePipeline object Y was created with GPUPipelineLayout.bindGroupLayouts A, D, C. Supposing the command encoding sequence has two dispatches:
  1. setBindGroup(0, ...)

  2. setBindGroup(1, ...)

  3. setBindGroup(2, ...)

  4. setPipeline(X)

  5. dispatch()

  6. setBindGroup(1, ...)

  7. setPipeline(Y)

  8. dispatch()

In this scenario, the user agent would have to re-bind the group slot 2 for the second dispatch, even though neither the GPUBindGroupLayout at index 2 of GPUPipelineLayout.bindGrouplayouts, or the GPUBindGroup at slot 2, change.

should this example and the note be moved to some "best practices" document?

Note: the expected usage of the GPUPipelineLayout is placing the most common and the least frequently changing bind groups at the "bottom" of the layout, meaning lower bind group slot numbers, like 0 or 1. The more frequently a bind group needs to change between draw calls, the higher its index should be. This general guideline allows the user agent to minimize state changes between draw calls, and consequently lower the CPU overhead.

8.3.1. Creation

A GPUPipelineLayout is created via GPUDevice.createPipelineLayout().

dictionary GPUPipelineLayoutDescriptor : GPUObjectDescriptorBase {
    required sequence<GPUBindGroupLayout> bindGroupLayouts;
};
createPipelineLayout(descriptor)

Creates a GPUPipelineLayout.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createPipelineLayout(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUPipelineLayoutDescriptor Description of the GPUPipelineLayout to create.

Returns: GPUPipelineLayout

  1. If any of the following conditions are unsatisfied:

    Then:

    1. Generate a GPUValidationError in the current scope with appropriate error message.

    2. Create a new invalid GPUPipelineLayout and return the result.

  2. Let pl be a new GPUPipelineLayout object.

  3. Set the pl.[[bindGroupLayouts]] to descriptor.bindGroupLayouts.

  4. Return pl.

there will be more limits applicable to the whole pipeline layout.

Note: two GPUPipelineLayout objects are considered equivalent for any usage if their internal [[bindGroupLayouts]] sequences contain GPUBindGroupLayout objects that are group-equivalent.

9. Shader Modules

9.1. GPUShaderModule

enum GPUCompilationMessageType {
    "error",
    "warning",
    "info"
};

[Serializable]
interface GPUCompilationMessage {
    readonly attribute DOMString message;
    readonly attribute GPUCompilationMessageType type;
    readonly attribute unsigned long long lineNum;
    readonly attribute unsigned long long linePos;
};

[Serializable]
interface GPUCompilationInfo {
    readonly attribute FrozenArray<GPUCompilationMessage> messages;
};

[Serializable]
interface GPUShaderModule {
    Promise<GPUCompilationInfo> compilationInfo();
};
GPUShaderModule includes GPUObjectBase;

GPUShaderModule is Serializable. It is a reference to an internal shader module object, and Serializable means that the reference can be copied between realms (threads/workers), allowing multiple realms to access it concurrently. Since GPUShaderModule is immutable, there are no race conditions.

9.1.1. Shader Module Creation

dictionary GPUShaderModuleDescriptor : GPUObjectDescriptorBase {
    required USVString code;
    object sourceMap;
};

sourceMap, if defined, MAY be interpreted as a source-map-v3 format. (https://sourcemaps.info/spec.html) Source maps are optional, but serve as a standardized way to support dev-tool integration such as source-language debugging.

createShaderModule(descriptor)

Creates a GPUShaderModule.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createShaderModule(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUShaderModuleDescriptor Description of the GPUShaderModule to create.

Returns: GPUShaderModule

Describe createShaderModule() algorithm steps.

9.1.2. Shader Module Compilation Information

compilationInfo()

Returns any messages generated during the GPUShaderModule's compilation.

Called on: GPUShaderModule this.

Returns: Promise<GPUCompilationInfo>

Describe compilationInfo() algorithm steps.

10. Pipelines

A pipeline, be it GPUComputePipeline or GPURenderPipeline, represents the complete function done by a combination of the GPU hardware, the driver, and the user agent, that process the input data in the shape of bindings and vertex buffers, and produces some output, like the colors in the output render targets.

Structurally, the pipeline consists of a sequence of programmable stages (shaders) and fixed-function states, such as the blending modes.

Note: Internally, depending on the target platform, the driver may convert some of the fixed-function states into shader code, and link it together with the shaders provided by the user. This linking is one of the reason the object is created as a whole.

This combination state is created as a single object (by GPUDevice.createComputePipeline() or GPUDevice.createRenderPipeline()), and switched as one (by GPUComputePassEncoder.setPipeline or GPURenderEncoderBase.setPipeline correspondingly).

10.1. Base pipelines

dictionary GPUPipelineDescriptorBase : GPUObjectDescriptorBase {
    GPUPipelineLayout layout;
};

interface mixin GPUPipelineBase {
    GPUBindGroupLayout getBindGroupLayout(unsigned long index);
};

GPUPipelineBase has the following internal slots:

[[layout]] of type GPUPipelineLayout.

The definition of the layout of resources which can be used with this.

GPUPipelineBase has the following methods:

getBindGroupLayout(index)

Gets a GPUBindGroupLayout that is compatible with the GPUPipelineBase's GPUBindGroupLayout at index.

Called on: GPUPipelineBase this.

Arguments:

Arguments for the GPUPipelineBase.getBindGroupLayout(index) method.
Parameter Type Nullable Optional Description
index unsigned long Index into the pipeline layout’s [[bindGroupLayouts]] sequence.

Returns: GPUBindGroupLayout

  1. If index is greater or equal to maxBindGroups:

    1. Throw a RangeError.

  2. If this is not valid:

    1. Return a new error GPUBindGroupLayout.

  3. Return a new GPUBindGroupLayout object that references the same internal object as this.[[layout]].[[bindGroupLayouts]][index].

Specify this more properly once we have internal objects for GPUBindGroupLayout. Alternatively only spec is as a new internal objects that’s group-equivalent

Note: Only returning new GPUBindGroupLayout objects ensures no synchronization is necessary between the Content timeline and the Device timeline.

10.1.1. Default pipeline layout

A GPUPipelineBase object that was created without a layout has a default layout created and used instead.

  1. Let groupDescs be a sequence of device.[[limits]].maxBindGroups new GPUBindGroupLayoutDescriptor objects.

  2. For each groupDesc in groupDescs:

    1. Set groupDesc.entries to an empty sequence.

  3. For each GPUProgrammableStageDescriptor stageDesc in the descriptor used to create the pipeline:

    1. Let stageInfo be the "reflection information" for stageDesc.

      Define the reflection information concept so that this spec can interface with the WGSL spec and get information what the interface is for a GPUShaderModule for a specific entrypoint.

    2. Let shaderStage be the GPUShaderStageFlags for stageDesc.entryPoint in stageDesc.module.

    3. For each resource resource in stageInfo’s resource interface:

      1. Let group be resource’s "group" decoration.

      2. Let binding be resource’s "binding" decoration.

      3. Let entry be a new GPUBindGroupLayoutEntry.

      4. Set entry.binding to binding.

      5. Set entry.visibility to shaderStage.

      6. If resource is for a sampler binding:

        1. Set entry.type to "sampler".

      7. If resource is for a comparison sampler binding:

        1. Set entry.type to "comparison-sampler".

      8. If resource is for a buffer binding:

        1. Set entry.hasDynamicOffset to false.

        2. Set entry.minBufferBindingSize to resource’s minimum buffer binding size.

          link to a definition for "minimum buffer binding size" in the "reflection information".

        3. If resource is for a uniform buffer:

          1. Set entry.type to "uniform-buffer".

        4. If resource is for a read-only storage buffer:

          1. Set entry.type to "readonly-storage-buffer".

        5. If resource is for a storage buffer:

          1. Set entry.type to "storage-buffer".

      9. If resource is for a texture binding:

        1. Set entry.textureComponentType to resource’s component type.

        2. Set entry.viewDimension to resource’s dimension.

        3. If resource is for a multisampled texture:

          1. Set entry.type to "multisampled-texture".

        4. If resource is for a single-sampled texture:

          1. Set entry.type to "sampled-texture".

        5. If resource is for a read-only storage texture:

          1. Set entry.type to "readonly-storage-texture".

          2. Set entry.storageTextureFormat to resource’s format.

        6. If resource is for a write-only storage texture:

          1. Set entry.type to "writeonly-storage-texture".

          2. Set entry.storageTextureFormat to resource’s format.

      10. If groupDescs[group] has an entry previousEntry with binding equal to binding:

        1. If entry has different visibility than previousEntry:

          1. Add the bits set in entry.visibility into previousEntry.visibility

        2. If entry has greater minBufferBindingSize than previousEntry:

          1. Set previousEntry.minBufferBindingSize to entry.minBufferBindingSize.

        3. If any other property is unequal between entry and previousEntry:

          1. Return null (which will cause the creation of the pipeline to fail).

      11. Else

        1. Append entry to groupDescs[group].

  4. Let groupLayouts be a new sequence.

  5. For each groupDesc in groupDescs:

    1. Append device.createBindGroupLayout()(groupDesc) to groupLayouts.

  6. Let desc be a new GPUPipelineLayoutDescriptor.

  7. Set desc.bindGroupLayouts to groupLayouts.

  8. Return device.createPipelineLayout()(desc).

This fills the pipeline layout with empty bindgroups. Revisit once the behavior of empty bindgroups is specified.

10.1.2. GPUProgrammableStageDescriptor

dictionary GPUProgrammableStageDescriptor {
    required GPUShaderModule module;
    required USVString entryPoint;
};

A GPUProgrammableStageDescriptor describes the entry point in the user-provided GPUShaderModule that controls one of the programmable stages of a pipeline.

validating GPUProgrammableStageDescriptor(stage, descriptor, layout) Arguments:
  1. If the descriptor.module is not a valid GPUShaderModule return false.

  2. If the descriptor.module doesn’t contain an entry point at stage named descriptor.entryPoint return false.

  3. For each binding that is statically used by the shader entry point, if the result of validating shader binding(binding, layout) is false, return false.

  4. Return true.

validating shader binding(binding, layout) Arguments:

Consider the shader binding annotation of bindIndex for the binding index and bindGroup for the bind group index.

Return true if all of the following conditions are satisfied:

  1. layout.[[bindGroupLayouts]][bindGroup] contains a GPUBindGroupLayoutEntry entry whose entry.binding == bindIndex.

  2. If entry.type is:

    "sampler"

    the binding is a non-comparison sampler

    "comparison-sampler"

    the binding is a comparison sampler

    "sampled-texture"

    the binding is a sampled texture with the component type of entry.textureComponentType and it has to have a sample count of 1.

    "multisampled-texture"

    the binding is a multisampled texture with the component type of entry.textureComponentType.

    "readonly-storage-texture"

    the binding is a read-only storage texture with format of entry.storageTextureFormat

    "writeonly-storage-texture"

    the binding is a writable storage texture with format of entry.storageTextureFormat

    "uniform-buffer"

    the binding is a uniform buffer

    "storage-buffer"

    the binding is a storage buffer

    "readonly-storage-buffer"

    the binding is a read-only storage buffer

  3. If entry.type is "sampled-texture", "readonly-storage-texture", or "writeonly-storage-texture", the shader view dimension of the texture has to match entry.viewDimension.

  4. If entry.minBufferBindingSize is not undefined:

    • If the last field of the corresponding structure defined in the shader has an unbounded array type, then the value of entry.minBufferBindingSize must be greater than or equal to the byte offset of that field plus the stride of the unbounded array.

    • If the corresponding shader structure doesn’t end with an unbounded array type, then the value of entry.minBufferBindingSize must be greater than or equal to the size of the structure.

is there a match/switch statement in bikeshed?

A resource binding is considered to be statically used by a shader entry point if and only if it’s reachable by the control flow graph of the shader module, starting at the entry point.

10.2. GPUComputePipeline

A GPUComputePipeline is a kind of pipeline that controls the compute shader stage, and can be used in GPUComputePassEncoder.

Compute inputs and outputs are all contained in the bindings, according to the given GPUPipelineLayout. The outputs correspond to "storage-buffer" and "writeonly-storage-texture" binding types.

Stages of a compute pipeline:

  1. Compute shader

[Serializable]
interface GPUComputePipeline {
};
GPUComputePipeline includes GPUObjectBase;
GPUComputePipeline includes GPUPipelineBase;

10.2.1. Creation

dictionary GPUComputePipelineDescriptor : GPUPipelineDescriptorBase {
    required GPUProgrammableStageDescriptor computeStage;
};
createComputePipeline(descriptor)

Creates a GPUComputePipeline.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createComputePipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePipelineDescriptor Description of the GPUComputePipeline to create.

Returns: GPUComputePipeline

If any of the following conditions are unsatisfied:

Then:

  1. Generate a GPUValidationError in the current scope with appropriate error message.

  2. Create a new invalid GPUComputePipeline and return the result.

createReadyComputePipeline(descriptor)

Creates a GPUComputePipeline. The returned Promise resolves when the created pipeline is ready to be used without additional delay.

If pipeline creation fails, the returned Promise resolves to an invalid GPUComputePipeline object.

Note: Use of this method is preferred whenever possible, as it prevents blocking the queue timeline work on pipeline compilation.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createReadyComputePipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePipelineDescriptor Description of the GPUComputePipeline to create.

Returns: Promise<GPUComputePipeline>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. Let pipeline be a new GPUComputePipeline created as if this.createComputePipeline() was called with descriptor;

    2. When pipeline is ready to be used, resolve promise with pipeline.

  3. Return promise.

10.3. GPURenderPipeline

A GPURenderPipeline is a kind of pipeline that controls the vertex and fragment shader stages, and can be used in GPURenderPassEncoder as well as GPURenderBundleEncoder.

Render pipeline inputs are:

Render pipeline outputs are:

Stages of a render pipeline:

  1. Vertex fetch, controlled by GPUVertexStateDescriptor

  2. Vertex shader

  3. Primitive assembly, controlled by GPUPrimitiveTopology

  4. Rasterization, controlled by GPURasterizationStateDescriptor

  5. Fragment shader

  6. Stencil test and operation, controlled by GPUDepthStencilStateDescriptor

  7. Depth test and write, controlled by GPUDepthStencilStateDescriptor

  8. Output merging, controlled by GPUColorStateDescriptor

we need a deeper description of these stages

[Serializable]
interface GPURenderPipeline {
};
GPURenderPipeline includes GPUObjectBase;
GPURenderPipeline includes GPUPipelineBase;

GPURenderPipeline has the following internal slots:

[[descriptor]], of type GPURenderPipelineDescriptor

The GPURenderPipelineDescriptor describing this pipeline.

All optional fields of GPURenderPipelineDescriptor are defined.

[[strip_index_format]], of type GPUIndexFormat?

The format index data this pipeline requires, initially undefined.

10.3.1. Creation

dictionary GPURenderPipelineDescriptor : GPUPipelineDescriptorBase {
    required GPUProgrammableStageDescriptor vertexStage;
    GPUProgrammableStageDescriptor fragmentStage;

    required GPUPrimitiveTopology primitiveTopology;
    GPURasterizationStateDescriptor rasterizationState = {};
    required sequence<GPUColorStateDescriptor> colorStates;
    GPUDepthStencilStateDescriptor depthStencilState;
    GPUVertexStateDescriptor vertexState = {};

    GPUSize32 sampleCount = 1;
    GPUSampleMask sampleMask = 0xFFFFFFFF;
    boolean alphaToCoverageEnabled = false;
};

Refactor the shape of the render pipeline descriptor to clearly enumerate the (ordered) list of pipeline stages. And start formalizing the spec text.

10.3.2. No Color Output

In no-color-output mode, pipeline does not produce any color attachment outputs, and the colorStates is expected to be empty.

The pipeline still performs rasterization and produces depth values based on the vertex position output. The depth testing and stencil operations can still be used.

10.3.3. Alpha to Coverage

In alpha-to-coverage mode, an additional alpha-to-coverage mask of MSAA samples is generated based on the alpha component of the fragment shader output value of the colorStates[0].

The algorithm of producing the extra mask is platform-dependent and can vary for different pixels. It guarantees that:

10.3.4. Sample Masking

The final sample mask for a pixel is computed as: rasterization mask & sampleMask & shader-output mask.

Only the lower sampleCount bits of the mask are considered.

If the least-significant bit at position N of the final sample mask has value of "0", the sample color outputs (corresponding to sample N) to all attachments of the fragment shader are discarded. Also, no depth test or stencil operations are executed on the relevant samples of the depth-stencil attachment.

Note: the color output for sample N is produced by the fragment shader execution with SV_SampleIndex == N for the current pixel. If the fragment shader doesn’t use this semantics, it’s only executed once per pixel.

The rasterization mask is produced by the rasterization stage, based on the shape of the rasterized polygon. The samples incuded in the shape get the relevant bits 1 in the mask.

The shader-output mask takes the output value of SV_Coverage semantics in the fragment shader. If the semantics is not statically used by the shader, and alphaToCoverageEnabled is enabled, the shader-output mask becomes the alpha-to-coverage mask. Otherwise, it defaults to 0xFFFFFFFF.

link to the semantics of SV_SampleIndex and SV_Coverage in WGSL spec.

createRenderPipeline(descriptor)

Creates a GPURenderPipeline.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createRenderPipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPipelineDescriptor Description of the GPURenderPipeline to create.

Returns: GPURenderPipeline

  1. Let pipeline be a new valid GPURenderPipeline object.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied:

      Then:

      1. Generate a GPUValidationError in the current scope with appropriate error message.

      2. Make pipeline invalid.

    2. Set pipeline.[[descriptor]] to descriptor.

    3. If descriptor.primitiveTopology is "line-strip" or "triangle-strip":

      1. Set pipeline.[[strip_index_format]] to descriptor.vertexState.indexFormat.

  3. Return pipeline.

need a proper limit for the maximum number of color targets.

need a more detailed validation of the render states.

need description of the render states.

createReadyRenderPipeline(descriptor)

Creates a GPURenderPipeline. The returned Promise resolves when the created pipeline is ready to be used without additional delay.

If pipeline creation fails, the returned Promise resolves to an invalid GPURenderPipeline object.

Note: Use of this method is preferred whenever possible, as it prevents blocking the queue timeline work on pipeline compilation.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createReadyRenderPipeline(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPipelineDescriptor Description of the GPURenderPipeline to create.

Returns: Promise<GPURenderPipeline>

  1. Let promise be a new promise.

  2. Issue the following steps on the Device timeline of this:

    1. Let pipeline be a new GPURenderPipeline created as if this.createRenderPipeline() was called with descriptor;

    2. When pipeline is ready to be used, resolve promise with pipeline.

  3. Return promise.

10.3.5. Primitive Topology

enum GPUPrimitiveTopology {
    "point-list",
    "line-list",
    "line-strip",
    "triangle-list",
    "triangle-strip"
};

10.3.6. Rasterization State

dictionary GPURasterizationStateDescriptor {
    GPUFrontFace frontFace = "ccw";
    GPUCullMode cullMode = "none";
    // Enable depth clamping (requires "depth-clamping" extension)
    boolean clampDepth = false;

    GPUDepthBias depthBias = 0;
    float depthBiasSlopeScale = 0;
    float depthBiasClamp = 0;
};
validating GPURasterizationStateDescriptor(device, descriptor)
  1. If device is lost return false.

  2. If descriptor.clampDepth is true and device.[[extensions]] doesn’t contain "depth-clamping", return false.

  3. Return true.

enum GPUFrontFace {
    "ccw",
    "cw"
};
enum GPUCullMode {
    "none",
    "front",
    "back"
};

10.3.7. Color State

dictionary GPUColorStateDescriptor {
    required GPUTextureFormat format;

    GPUBlendDescriptor alphaBlend = {};
    GPUBlendDescriptor colorBlend = {};
    GPUColorWriteFlags writeMask = 0xF;  // GPUColorWrite.ALL
};
typedef [EnforceRange] unsigned long GPUColorWriteFlags;
interface GPUColorWrite {
    const GPUFlagsConstant RED   = 0x1;
    const GPUFlagsConstant GREEN = 0x2;
    const GPUFlagsConstant BLUE  = 0x4;
    const GPUFlagsConstant ALPHA = 0x8;
    const GPUFlagsConstant ALL   = 0xF;
};
10.3.7.1. Blend State
dictionary GPUBlendDescriptor {
    GPUBlendFactor srcFactor = "one";
    GPUBlendFactor dstFactor = "zero";
    GPUBlendOperation operation = "add";
};
enum GPUBlendFactor {
    "zero",
    "one",
    "src-color",
    "one-minus-src-color",
    "src-alpha",
    "one-minus-src-alpha",
    "dst-color",
    "one-minus-dst-color",
    "dst-alpha",
    "one-minus-dst-alpha",
    "src-alpha-saturated",
    "blend-color",
    "one-minus-blend-color"
};
enum GPUBlendOperation {
    "add",
    "subtract",
    "reverse-subtract",
    "min",
    "max"
};

10.3.8. Depth/Stencil State

dictionary GPUDepthStencilStateDescriptor {
    required GPUTextureFormat format;

    boolean depthWriteEnabled = false;
    GPUCompareFunction depthCompare = "always";

    GPUStencilStateFaceDescriptor stencilFront = {};
    GPUStencilStateFaceDescriptor stencilBack = {};

    GPUStencilValue stencilReadMask = 0xFFFFFFFF;
    GPUStencilValue stencilWriteMask = 0xFFFFFFFF;
};
dictionary GPUStencilStateFaceDescriptor {
    GPUCompareFunction compare = "always";
    GPUStencilOperation failOp = "keep";
    GPUStencilOperation depthFailOp = "keep";
    GPUStencilOperation passOp = "keep";
};
enum GPUStencilOperation {
    "keep",
    "zero",
    "replace",
    "invert",
    "increment-clamp",
    "decrement-clamp",
    "increment-wrap",
    "decrement-wrap"
};

10.3.9. Vertex State

enum GPUIndexFormat {
    "uint16",
    "uint32"
};

The index format determines both the data type of index values in a buffer and, when used with strip primitive topologies ("line-strip" or "triangle-strip") also specifies the primitive restart value. The primitive restart value indicates which index value indicates that a new primitive should be started rather than continuing to construct the triangle strip with the prior indexed vertices.

GPURenderPipelineDescriptors that specify a strip primitive topology must not have the indexFormat set to undefined so that the primitive restart value that will be used is known at pipline creation time.

Index format Primitive restart value
"uint16" 0xFFFF
"uint32" 0xFFFFFFFF
10.3.9.1. Vertex Formats

The name of the format specifies the data type of the component, the number of values, and whether the data is normalized.

If no number of values is given in the name, a single value is provided. If the format has the -bgra suffix, it means the values are arranged as blue, green, red and alpha values.

enum GPUVertexFormat {
    "uchar2",
    "uchar4",
    "char2",
    "char4",
    "uchar2norm",
    "uchar4norm",
    "char2norm",
    "char4norm",
    "ushort2",
    "ushort4",
    "short2",
    "short4",
    "ushort2norm",
    "ushort4norm",
    "short2norm",
    "short4norm",
    "half2",
    "half4",
    "float",
    "float2",
    "float3",
    "float4",
    "uint",
    "uint2",
    "uint3",
    "uint4",
    "int",
    "int2",
    "int3",
    "int4"
};
enum GPUInputStepMode {
    "vertex",
    "instance"
};
dictionary GPUVertexStateDescriptor {
    GPUIndexFormat indexFormat;
    sequence<GPUVertexBufferLayoutDescriptor?> vertexBuffers = [];
};

A vertex buffer is, conceptually, a view into buffer memory as an array of structures. arrayStride is the stride, in bytes, between elements of that array. Each element of a vertex buffer is like a structure with a memory layout defined by its attributes, which describe the members of the structure.

Each GPUVertexAttributeDescriptor describes its format and its offset, in bytes, within the structure.

Each attribute appears as a separate input in a vertex shader, each bound by a numeric location, which is specified by shaderLocation. Every location must be unique within the GPUVertexStateDescriptor.

dictionary GPUVertexBufferLayoutDescriptor {
    required GPUSize64 arrayStride;
    GPUInputStepMode stepMode = "vertex";
    required sequence<GPUVertexAttributeDescriptor> attributes;
};
dictionary GPUVertexAttributeDescriptor {
    required GPUVertexFormat format;
    required GPUSize64 offset;

    required GPUIndex32 shaderLocation;
};
validating GPUVertexBufferLayoutDescriptor(descriptor, vertexStage) Arguments:

Return true, if and only if, all of the following conditions are satisfied:

  1. descriptor.attributes.length is less than or equal to 16.

  2. descriptor.arrayStride is less then or equal to 2048.

  3. Any attribute at in the list descriptor.attributes has at.{{GPUVertexAttributeDescriptor/offset} + sizeOf(at.format less or equal to descriptor.arrayStride.

  4. For every vertex attribute in the shader reflection of vertexStage.module that is know to be statically used by vertexStage.entryPoint, there is a corresponding at element of descriptor.attributes that:

    1. The shader format is at.format.

    2. The shader location is at.shaderLocation.

add a limit to the number of vertex attributes

validating GPUVertexStateDescriptor(descriptor, vertexStage) Arguments:

Return true, if and only if, all of the following conditions are satisfied:

  1. descriptor.vertexBuffers.length is less than or equal to 8

  2. Each vertexBuffer layout descriptor in the list descriptor.vertexBuffers passes validating GPUVertexBufferLayoutDescriptor(vertexBuffer, vertexStage)

  3. Each at in the union of all GPUVertexAttributeDescriptor across descriptor.vertexBuffers has a distinct at.shaderLocation value.

add a limit to the number of vertex buffers

11. Command Buffers

Command buffers are pre-recorded lists of GPU commands that can be submitted to a GPUQueue for execution. Each GPU command represents a task to be performed on the GPU, such as setting state, drawing, copying resources, etc.

11.1. GPUCommandBuffer

interface GPUCommandBuffer {
    readonly attribute Promise<double> executionTime;
};
GPUCommandBuffer includes GPUObjectBase;

GPUCommandBuffer has the following attributes:

executionTime of type Promise<, of type Promise<double>, readonlydouble>, readonly

The total time, in seconds, that the GPU took to execute this command buffer.

Note: If measureExecutionTime is true, this resolves after the command buffer executes. Otherwise, this rejects with an OperationError.

Specify the creation and resolution of the promise.

In finish(), it should be specified that a new promise is created and stored in this attribute. The promise starts rejected if measureExecutionTime is false. If the finish() fails, then the promise resolves to 0.

In submit(), it should be specified that (if measureExecutionTime is set), work is issued to read back the execution time, and, when that completes, the promise is resolved with that value. If the submit() fails, then the promise resolves to 0.

GPUCommandBuffer has the following internal slots:

[[command_list]] of type list<GPU command>.

A list of GPU commands to be executed on the Queue timeline when this command buffer is submitted.

11.1.1. Creation

dictionary GPUCommandBufferDescriptor : GPUObjectDescriptorBase {
};

12. Command Encoding

12.1. GPUCommandEncoder

interface GPUCommandEncoder {
    GPURenderPassEncoder beginRenderPass(GPURenderPassDescriptor descriptor);
    GPUComputePassEncoder beginComputePass(optional GPUComputePassDescriptor descriptor = {});

    undefined copyBufferToBuffer(
        GPUBuffer source,
        GPUSize64 sourceOffset,
        GPUBuffer destination,
        GPUSize64 destinationOffset,
        GPUSize64 size);

    undefined copyBufferToTexture(
        GPUBufferCopyView source,
        GPUTextureCopyView destination,
        GPUExtent3D copySize);

    undefined copyTextureToBuffer(
        GPUTextureCopyView source,
        GPUBufferCopyView destination,
        GPUExtent3D copySize);

    undefined copyTextureToTexture(
        GPUTextureCopyView source,
        GPUTextureCopyView destination,
        GPUExtent3D copySize);

    undefined pushDebugGroup(USVString groupLabel);
    undefined popDebugGroup();
    undefined insertDebugMarker(USVString markerLabel);

    undefined writeTimestamp(GPUQuerySet querySet, GPUSize32 queryIndex);

    undefined resolveQuerySet(
        GPUQuerySet querySet,
        GPUSize32 firstQuery,
        GPUSize32 queryCount,
        GPUBuffer destination,
        GPUSize64 destinationOffset);

    GPUCommandBuffer finish(optional GPUCommandBufferDescriptor descriptor = {});
};
GPUCommandEncoder includes GPUObjectBase;

GPUCommandEncoder has the following internal slots:

[[command_list]] of type list<GPU command>.

A list of GPU command to be executed on the Queue timeline when the GPUCommandBuffer this encoder produces is submitted.

[[state]] of type encoder state.

The current state of the GPUCommandEncoder, initially set to open.

[[debug_group_stack]] of type stack<USVString>.

A stack of active debug group labels.

Each GPUCommandEncoder has a current encoder state on the Content timeline which may be one of the following:

"open"

Indicates the GPUCommandEncoder is available to begin new operations. The [[state]] is open any time the GPUCommandEncoder is valid and has no active GPURenderPassEncoder or GPUComputePassEncoder.

"encoding a render pass"

Indicates the GPUCommandEncoder has an active GPURenderPassEncoder. The [[state]] becomes encoding a render pass once beginRenderPass() is called sucessfully until endPass() is called on the returned GPURenderPassEncoder, at which point the [[state]] (if the encoder is still valid) reverts to open.

"encoding a compute pass"

Indicates the GPUCommandEncoder has an active GPUComputePassEncoder. The [[state]] becomes encoding a compute pass once beginComputePass() is called sucessfully until endPass() is called on the returned GPUComputePassEncoder, at which point the [[state]] (if the encoder is still valid) reverts to open.

"closed"

Indicates the GPUCommandEncoder is no longer available for any operations. The [[state]] becomes closed once finish() is called or the GPUCommandEncoder otherwise becomes invalid.

12.1.1. Creation

dictionary GPUCommandEncoderDescriptor : GPUObjectDescriptorBase {
    boolean measureExecutionTime = false;

    // TODO: reusability flag?
};
measureExecutionTime, of type boolean, defaulting to false

Enable measurement of the GPU execution time of the entire command buffer.

createCommandEncoder(descriptor)

Creates a GPUCommandEncoder.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createCommandEncoder(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUCommandEncoderDescriptor Description of the GPUCommandEncoder to create.

Returns: GPUCommandEncoder

Describe createCommandEncoder() algorithm steps.

12.2. Pass Encoding

beginRenderPass(descriptor)

Begins encoding a render pass described by descriptor.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.beginRenderPass(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderPassDescriptor Description of the GPURenderPassEncoder to create.

Returns: GPURenderPassEncoder

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Set this.[[state]] to encoding a render pass.

  3. For each colorAttachment in descriptor.colorAttachments:

    1. The texture subresource seen by colorAttachment.attachment is considered to be used as attachment for the duration of the render pass.

  4. Let depthStencilAttachment be descriptor.depthStencilAttachment.

  5. If depthStencilAttachment is not null:

    1. if depthStencilAttachment.depthReadOnly and stencilReadOnly are set

      1. The texture subresources seen by depthStencilAttachment.attachment are considered to be used as attachment-read for the duration of the render pass.

    2. Else, the texture subresource seen by depthStencilAttachment.attachment is considered to be used as attachment for the duration of the render pass.

specify the behavior of read-only depth/stencil Issue: Enqueue attachment loads (with loadOp clear).

beginComputePass(descriptor)

Begins encoding a compute pass described by descriptor.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.beginComputePass(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUComputePassDescriptor

Returns: GPUComputePassEncoder

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Set this.[[state]] to encoding a compute pass.

12.3. Copy Commands

12.3.1. GPUTextureDataLayout

dictionary GPUTextureDataLayout {
    GPUSize64 offset = 0;
    GPUSize32 bytesPerRow;
    GPUSize32 rowsPerImage;
};

A GPUTextureDataLayout is a layout of images within some linear memory. It’s used when copying data between a texture and a buffer, or when scheduling a write into a texture from the GPUQueue.

Operations that copy between byte arrays and textures always work with rows of texel blocks, which we’ll call block rows. It’s not possible to update only a part of a texel block.

Define images more precisely. In particular, define them as being comprised of texel blocks.

Define the exact copy semantics, by reference to common algorithms shared by the copy methods.

bytesPerRow, of type GPUSize32

The stride, in bytes, between the beginning of each block row and the subsequent block row.

Required if there are multiple block rows (i.e. the height or depth is more than one block).

rowsPerImage, of type GPUSize32

Number of block rows per single image of the texture. rowsPerImage × bytesPerRow is the stride, in bytes, between the beginning of each image of data and the subsequent image.

Required if there are multiple images (i.e. the depth is more than one).

12.3.2. GPUBufferCopyView

dictionary GPUBufferCopyView : GPUTextureDataLayout {
    required GPUBuffer buffer;
};

A GPUBufferCopyView contains the actual texture data placed in a buffer according to GPUTextureDataLayout.

validating GPUBufferCopyView

Arguments:

Returns: boolean

Return true if and only if all of the following conditions are satisfied:

12.3.3. GPUTextureCopyView

dictionary GPUTextureCopyView {
    required GPUTexture texture;
    GPUIntegerCoordinate mipLevel = 0;
    GPUOrigin3D origin = {};
};

A GPUTextureCopyView is a view of a sub-region of one or multiple contiguous texture subresources with the initial offset GPUOrigin3D in texels, used when copying data from or to a GPUTexture.

validating GPUTextureCopyView

Arguments:

Returns: boolean

Let:

Return true if and only if all of the following conditions apply:

Define the copies with 1d and 3d textures. <https://github.com/gpuweb/gpuweb/issues/69>

12.3.4. GPUImageBitmapCopyView

dictionary GPUImageBitmapCopyView {
    required ImageBitmap imageBitmap;
    GPUOrigin2D origin = {};
};
copyBufferToBuffer(source, sourceOffset, destination, destinationOffset, size)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of a GPUBuffer to a sub-region of another GPUBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyBufferToBuffer(source, sourceOffset, destination, destinationOffset, size) method.
Parameter Type Nullable Optional Description
source GPUBuffer The GPUBuffer to copy from.
sourceOffset GPUSize64 Offset in bytes into source to begin copying from.
destination GPUBuffer The GPUBuffer to copy to.
destinationOffset GPUSize64 Offset in bytes into destination to place the copied data.
size GPUSize64 Bytes to copy.

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

Define the state machine for GPUCommandEncoder. <https://github.com/gpuweb/gpuweb/issues/21>

figure out how to handle overflows in the spec. <https://github.com/gpuweb/gpuweb/issues/69>

12.3.5. Copy Between Buffer and Texture

WebGPU provides copyBufferToTexture() for buffer-to-texture copies and copyTextureToBuffer() for texture-to-buffer copies.

The following definitions and validation rules apply to both copyBufferToTexture() and copyTextureToBuffer().

textureCopyView subresource size and Valid Texture Copy Range also applies to copyTextureToTexture().

textureCopyView subresource size

Arguments:

Returns: GPUExtent3D

The textureCopyView subresource size of textureCopyView is calculated as follows:

Its width, height and depth are the width, height, and depth, respectively, of the physical size of textureCopyView.texture subresource at mipmap level textureCopyView.mipLevel.

define this as an algorithm with (texture, mipmapLevel) parameters and use the call syntax instead of referring to the definition by label.

validating linear texture data(layout, byteSize, format, copyExtent)

Arguments:

GPUTextureDataLayout layout

Layout of the linear texture data.

GPUSize64 byteSize

Total size of the linear data, in bytes.

GPUTextureFormat format

Format of the texture.

GPUExtent3D copyExtent

Extent of the texture to copy.

  1. Let blockWidth, blockHeight, and blockSize be the texel block width, height, and size of format.

  2. It is assumed that copyExtent.width is a multiple of blockWidth and copyExtent.height is a multiple of blockHeight. Let:

    • widthInBlocks be copyExtent.width ÷ blockWidth.

    • heightInBlocks be copyExtent.height ÷ blockHeight.

    • bytesInACompleteRow be blockSize × widthInBlocks.

  3. Fail if the following conditions are not satisfied:

    • If heightInBlocks > 1, layout.bytesPerRow must be specified.

    • If copyExtent.depth > 1, layout.bytesPerRow and layout.rowsPerImage must be specified.

    • If specified, layout.bytesPerRow must be greater than or equal to bytesInACompleteRow.

    • If specified, layout.rowsPerImage must be greater than or equal to heightInBlocks.

  4. Let requiredBytesInCopy be widthInBlocks × blockSize.

  5. If heightInBlocks > 1, add layout.bytesPerRow × (heightInBlocks − 1) to requiredBytesInCopy.

  6. If copyExtent.depth > 1, add layout.bytesPerRow × layout.rowsPerImage × (copyExtent.depth − 1) to requiredBytesInCopy.

  7. Fail if the following conditions are not satisfied:

    • layout.offset + requiredBytesInCopy must be smaller than or equal to byteSize.

    • layout.offset must be a multiple of blockSize.

Valid Texture Copy Range

Given a GPUTextureCopyView textureCopyView and a GPUExtent3D copySize, let

The following validation rules apply:

Define the copies with 1d and 3d textures. <https://github.com/gpuweb/gpuweb/issues/69>

Additional restrictions on rowsPerImage if needed. <https://github.com/gpuweb/gpuweb/issues/537>

Define the copies with "depth24plus", "depth24plus-stencil8", and "stencil8". <https://github.com/gpuweb/gpuweb/issues/652>

convert "Valid Texture Copy Range" into an algorithm with parameters, similar to "validating linear texture data"

copyBufferToTexture(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of a GPUBuffer to a sub-region of one or multiple continuous texture subresources.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyBufferToTexture(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUBufferCopyView Combined with copySize, defines the region of the source buffer.
destination GPUTextureCopyView Combined with copySize, defines the region of the destination texture subresource.
copySize GPUExtent3D

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

copyTextureToBuffer(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of one or multiple continuous texture subresourcesto a sub-region of a GPUBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyTextureToBuffer(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUTextureCopyView Combined with copySize, defines the region of the source texture subresources.
destination GPUBufferCopyView Combined with copySize, defines the region of the destination buffer.
copySize GPUExtent3D

Returns: undefined

If any of the following conditions are unsatisfied, generate a validation error and stop.

copyTextureToTexture(source, destination, copySize)

Encode a command into the GPUCommandEncoder that copies data from a sub-region of one or multiple contiguous texture subresources to another sub-region of one or multiple continuous texture subresources.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.copyTextureToTexture(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUTextureCopyView Combined with copySize, defines the region of the source texture subresources.
destination GPUTextureCopyView Combined with copySize, defines the region of the destination texture subresources.
copySize GPUExtent3D

Returns: undefined

  1. Let copy of the whole subresource be the command this.copyTextureToTexture() whose parameters source, destination and copySize meet the following conditions:

  2. If any of the following conditions are unsatisfied, generate a validation error and stop.

The set of subresources for texture copy(textureCopyView, copySize) is the set containing:

12.4. Debug Markers

Both command encoders and programmable pass encoders provide methods to apply debug labels to groups of commands or insert a single label into the command sequence. Debug groups can be nested to create a hierarchy of labeled commands. These labels may be passed to the native API backends for tooling, may be used by the user agent’s internal tooling, or may be a no-op when such tooling is not available or applicable.

Debug groups in a GPUCommandEncoder or GPUProgrammablePassEncoder must be well nested.

pushDebugGroup(groupLabel)

Marks the beginning of a labeled group of commands for the GPUCommandEncoder.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.pushDebugGroup(groupLabel) method.
Parameter Type Nullable Optional Description
groupLabel USVString The label for the command group.

Returns: undefined

Issue the following steps on the Device timeline of this:

popDebugGroup()

Marks the end of a labeled group of commands for the GPUCommandEncoder.

Called on: GPUCommandEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

insertDebugMarker(markerLabel)

Marks the end of a labeled group of commands for the GPUCommandEncoder.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.insertDebugMarker(markerLabel) method.
Parameter Type Nullable Optional Description
markerLabel USVString The label to insert.

Returns: undefined

Issue the following steps on the Device timeline of this:

  • If any of the following conditions are unsatisfied, make this invalid and stop.

12.5. Queries

writeTimestamp(querySet, queryIndex)
Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.writeTimestamp(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

Describe writeTimestamp() algorithm steps.

resolveQuerySet(querySet, firstQuery, queryCount, destination, destinationOffset)
Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.resolveQuerySet(querySet, firstQuery, queryCount, destination, destinationOffset) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
firstQuery GPUSize32
queryCount GPUSize32
destination GPUBuffer
destinationOffset GPUSize64

Returns: undefined

If any of the following conditions are unsatisfied, generate a GPUValidationError and stop.

  • this.[[state]] is open.

  • querySet is valid to use with this.

  • destination is valid to use with this.

  • destination.[[usage]] contains QUERY_RESOLVE.

  • firstQuery is less than the number of queries in querySet.

  • (firstQuery + queryCount) is less than or equal to the number of queries in querySet.

  • destinationOffset is a multiple of 8.

  • destinationOffset + 8 × queryCountdestination.[[size]].

Describe resolveQuerySet() algorithm steps.

12.6. Finalization

A GPUCommandBuffer containing the commands recorded by the GPUCommandEncoder can be created by calling finish(). Once finish() has been called the command encoder can no longer be used.

finish(descriptor)

Completes recording of the commands sequence and returns a corresponding GPUCommandBuffer.

Called on: GPUCommandEncoder this.

Arguments:

Arguments for the GPUCommandEncoder.finish(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUCommandBufferDescriptor

Returns: GPUCommandBuffer

  1. Let commandBuffer be a new GPUCommandBuffer.

  2. Issue the following steps on the Device timeline of this:

    1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    2. Set this.[[state]] to closed.

    3. Let commandBuffer.[[command_list]] be a clone of this.[[command_list]].

  3. Return commandBuffer.

13. Programmable Passes

interface mixin GPUProgrammablePassEncoder {
    undefined setBindGroup(GPUIndex32 index, GPUBindGroup bindGroup,
                      optional sequence<GPUBufferDynamicOffset> dynamicOffsets = []);

    undefined setBindGroup(GPUIndex32 index, GPUBindGroup bindGroup,
                      Uint32Array dynamicOffsetsData,
                      GPUSize64 dynamicOffsetsDataStart,
                      GPUSize32 dynamicOffsetsDataLength);

    undefined pushDebugGroup(USVString groupLabel);
    undefined popDebugGroup();
    undefined insertDebugMarker(USVString markerLabel);
};

GPUProgrammablePassEncoder has the following internal slots:

[[command_encoder]] of type GPUCommandEncoder.

The GPUCommandEncoder that created this programmable pass.

[[debug_group_stack]] of type stack<USVString>.

A stack of active debug group labels.

[[bind_groups]], of type ordered map<GPUIndex32, GPUBindGroup>

The current GPUBindGroup for each index, initially empty.

13.1. Bind Groups

setBindGroup(index, bindGroup, dynamicOffsets)

Sets the current GPUBindGroup for the given index.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.setBindGroup(index, bindGroup, dynamicOffsets) method.
Parameter Type Nullable Optional Description
index GPUIndex32 The index to set the bind group at.
bindGroup GPUBindGroup Bind group to use for subsequent render or compute commands.

Resolve bikeshed conflict when using argumentdef with overloaded functions that prevents us from defining dynamicOffsets.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Set this.[[bind_groups]][index] to be bindGroup.

setBindGroup(index, bindGroup, dynamicOffsetsData, dynamicOffsetsDataStart, dynamicOffsetsDataLength)

Sets the current GPUBindGroup for the given index, specifying dynamic offsets as a subset of a Uint32Array.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.setBindGroup(index, bindGroup, dynamicOffsetsData, dynamicOffsetsDataStart, dynamicOffsetsDataLength) method.
Parameter Type Nullable Optional Description
index GPUIndex32 The index to set the bind group at.
bindGroup GPUBindGroup Bind group to use for subsequent render or compute commands.
dynamicOffsetsData Uint32Array Array containing buffer offsets in bytes for each entry in bindGroup with marked as hasDynamicOffset.
dynamicOffsetsDataStart GPUSize64 Offset in elements into dynamicOffsetsData where the buffer offset data begins.
dynamicOffsetsDataLength GPUSize32 Number of buffer offsets to read from dynamicOffsetsData.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Set this.[[bind_groups]][index] to be bindGroup.

To Iterate over each dynamic binding offset in a given GPUBindGroup bindGroup with a given list of steps to be executed for each dynamic offset:
  1. Let dynamicOffsetIndex be 0.

  2. Let layout be bindGroup.[[layout]].

  3. For each GPUBindGroupEntry entry in bindGroup.[[entries]]:

    1. Let bindingDescriptor be the GPUBindGroupLayoutEntry at layout.[[entryMap]][entry.binding]:

    2. If bindingDescriptor.hasDynamicOffset is true:

      1. Let bufferBinding be entry.resource.

      2. Let minBufferBindingSize be bindingDescriptor.minBufferBindingSize.

      3. Call steps with bufferBinding, minBufferBindingSize, and dynamicOffsetIndex.

      4. Let dynamicOffsetIndex be dynamicOffsetIndex + 1

Validate encoder bind groups(encoder, pipeline)

Arguments:

GPUProgrammablePassEncoder encoder

Encoder who’s bind groups are being validated.

GPUPipelineBase pipeline

Pipline to validate encoders bind groups are compatible with.

If any of the following conditions are unsatisfied, return false:

Check buffer bindings against minBufferBindingSize if present.

Otherwise return true.

13.2. Debug Markers

Debug marker methods for programmable pass encoders provide the same functionality as command encoder debug markers while recording a programmable pass.

pushDebugGroup(groupLabel)

Marks the beginning of a labeled group of commands for the GPUProgrammablePassEncoder.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.pushDebugGroup(groupLabel) method.
Parameter Type Nullable Optional Description
groupLabel USVString The label for the command group.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. Push groupLabel onto this.[[debug_group_stack]].

popDebugGroup()

Marks the end of a labeled group of commands for the GPUProgrammablePassEncoder.

Called on: GPUProgrammablePassEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Pop an entry off of this.[[debug_group_stack]].

insertDebugMarker(markerLabel)

Inserts a single debug marker label into the GPUProgrammablePassEncoder's commands sequence.

Called on: GPUProgrammablePassEncoder this.

Arguments:

Arguments for the GPUProgrammablePassEncoder.insertDebugMarker(markerLabel) method.
Parameter Type Nullable Optional Description
markerLabel USVString The label to insert.

Returns: undefined

14. Compute Passes

14.1. GPUComputePassEncoder

interface GPUComputePassEncoder {
    undefined setPipeline(GPUComputePipeline pipeline);
    undefined dispatch(GPUSize32 x, optional GPUSize32 y = 1, optional GPUSize32 z = 1);
    undefined dispatchIndirect(GPUBuffer indirectBuffer, GPUSize64 indirectOffset);

    undefined beginPipelineStatisticsQuery(GPUQuerySet querySet, GPUSize32 queryIndex);
    undefined endPipelineStatisticsQuery();

    undefined writeTimestamp(GPUQuerySet querySet, GPUSize32 queryIndex);

    undefined endPass();
};
GPUComputePassEncoder includes GPUObjectBase;
GPUComputePassEncoder includes GPUProgrammablePassEncoder;

GPUComputePassEncoder has the following internal slots:

[[pipeline]], of type GPUComputePipeline

The current GPUComputePipeline, initially null.

14.1.1. Creation

dictionary GPUComputePassDescriptor : GPUObjectDescriptorBase {
};

14.1.2. Dispatch

setPipeline(pipeline)

Sets the current GPUComputePipeline.

Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.setPipeline(pipeline) method.
Parameter Type Nullable Optional Description
pipeline GPUComputePipeline The compute pipeline to use for subsequent dispatch commands.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Set this.[[pipeline]] to be pipeline.

dispatch(x, y, z)

Dispatch work to be performed with the current GPUComputePipeline.

Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.dispatch(x, y, z) method.
Parameter Type Nullable Optional Description
x GPUSize32 X dimension of the grid of workgroups to dispatch.
y GPUSize32 Y dimension of the grid of workgroups to dispatch.
z GPUSize32 Z dimension of the grid of workgroups to dispatch.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Append a GPU command to this.[[command_encoder]].[[command_list]] that captures the GPUComputePassEncoder state of this as passState and, when executed, issues the following steps on the appropriate Queue timeline:

    1. Dispatch a grid of workgroups with dimensions [x, y, z] with passState.[[pipeline]] using passState.[[bind_groups]].

dispatchIndirect(indirectBuffer, indirectOffset)

Dispatch work to be performed with the current GPUComputePipeline using parameters read from a GPUBuffer.

The indirect dispatch parameters encoded in the buffer must be a tightly packed block of three 32-bit unsigned integer values (12 bytes total), given in the same order as the arguments for dispatch(). For example:

        let dispatchIndirectParameters = new Uint32Array(3);
        dispatchIndirectParameters[0] = x;
        dispatchIndirectParameters[1] = y;
        dispatchIndirectParameters[2] = z;
Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.dispatchIndirect(indirectBuffer, indirectOffset) method.
Parameter Type Nullable Optional Description
indirectBuffer GPUBuffer Buffer containing the indirect dispatch parameters.
indirectOffset GPUSize64 Offset in bytes into indirectBuffer where the dispatch data begins.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Add indirectBuffer to the usage scope as INDIRECT.

14.1.3. Queries

beginPipelineStatisticsQuery(querySet, queryIndex)
Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.beginPipelineStatisticsQuery(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

Describe beginPipelineStatisticsQuery() algorithm steps.

endPipelineStatisticsQuery()
Called on: GPUComputePassEncoder this.

Returns: undefined

Describe endPipelineStatisticsQuery() algorithm steps.

writeTimestamp(querySet, queryIndex)
Called on: GPUComputePassEncoder this.

Arguments:

Arguments for the GPUComputePassEncoder.writeTimestamp(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

Describe writeTimestamp() algorithm steps.

14.1.4. Finalization

The compute pass encoder can be ended by calling endPass() once the user has finished recording commands for the pass. Once endPass() has been called the compute pass encoder can no longer be used.

endPass()

Completes recording of the compute pass commands sequence.

Called on: GPUComputePassEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    Add remaining validation.

15. Render Passes

15.1. GPURenderPassEncoder

interface mixin GPURenderEncoderBase {
    undefined setPipeline(GPURenderPipeline pipeline);

    undefined setIndexBuffer(GPUBuffer buffer, GPUIndexFormat indexFormat, optional GPUSize64 offset = 0, optional GPUSize64 size = 0);
    undefined setVertexBuffer(GPUIndex32 slot, GPUBuffer buffer, optional GPUSize64 offset = 0, optional GPUSize64 size = 0);

    undefined draw(GPUSize32 vertexCount, optional GPUSize32 instanceCount = 1,
              optional GPUSize32 firstVertex = 0, optional GPUSize32 firstInstance = 0);
    undefined drawIndexed(GPUSize32 indexCount, optional GPUSize32 instanceCount = 1,
                     optional GPUSize32 firstIndex = 0,
                     optional GPUSignedOffset32 baseVertex = 0,
                     optional GPUSize32 firstInstance = 0);

    undefined drawIndirect(GPUBuffer indirectBuffer, GPUSize64 indirectOffset);
    undefined drawIndexedIndirect(GPUBuffer indirectBuffer, GPUSize64 indirectOffset);
};

interface GPURenderPassEncoder {
    undefined setViewport(float x, float y,
                     float width, float height,
                     float minDepth, float maxDepth);

    undefined setScissorRect(GPUIntegerCoordinate x, GPUIntegerCoordinate y,
                        GPUIntegerCoordinate width, GPUIntegerCoordinate height);

    undefined setBlendColor(GPUColor color);
    undefined setStencilReference(GPUStencilValue reference);

    undefined beginOcclusionQuery(GPUSize32 queryIndex);
    undefined endOcclusionQuery();

    undefined beginPipelineStatisticsQuery(GPUQuerySet querySet, GPUSize32 queryIndex);
    undefined endPipelineStatisticsQuery();

    undefined writeTimestamp(GPUQuerySet querySet, GPUSize32 queryIndex);

    undefined executeBundles(sequence<GPURenderBundle> bundles);
    undefined endPass();
};
GPURenderPassEncoder includes GPUObjectBase;
GPURenderPassEncoder includes GPUProgrammablePassEncoder;
GPURenderPassEncoder includes GPURenderEncoderBase;

GPURenderEncoderBase has the following internal slots:

[[pipeline]], of type GPURenderPipeline

The current GPURenderPipeline, initially null.

[[index_buffer]], of type GPUBuffer

The current buffer to read index data from, initially null.

[[index_format]], of type GPUIndexFormat

The format of the index data in [[index_buffer]].

[[vertex_buffers]], of type ordered map<slot, GPUBuffer>

The current GPUBuffers to read vertex data from for each slot, initially empty.

GPURenderPassEncoder has the following internal slots:

[[attachment_size]]

Set to the following extents:

  • width, height = the dimensions of the pass’s render attachments

When a GPURenderPassEncoder is created, it has the following default state:

15.1.1. Creation

dictionary GPURenderPassDescriptor : GPUObjectDescriptorBase {
    required sequence<GPURenderPassColorAttachmentDescriptor> colorAttachments;
    GPURenderPassDepthStencilAttachmentDescriptor depthStencilAttachment;
    GPUQuerySet occlusionQuerySet;
};
colorAttachments, of type sequence<GPURenderPassColorAttachmentDescriptor>

The set of GPURenderPassColorAttachmentDescriptor values in this sequence defines which color attachments will be output to when executing this render pass.

depthStencilAttachment, of type GPURenderPassDepthStencilAttachmentDescriptor

The GPURenderPassDepthStencilAttachmentDescriptor value that defines the depth/stencil attachment that will be output to and tested against when executing this render pass.

occlusionQuerySet, of type GPUQuerySet

Describe this dictionary member

GPURenderPassDescriptor Valid Usage

Given a GPURenderPassDescriptor this the following validation rules apply:

  1. this.colorAttachments.length must be less than or equal to the maximum color attachments.

  2. this.colorAttachments.length must greater than 0 or this.depthStencilAttachment must not be null.

  3. For each colorAttachment in this.colorAttachments:

    1. colorAttachment must meet the GPURenderPassColorAttachmentDescriptor Valid Usage rules.

  4. If this.depthStencilAttachment is not null:

    1. this.depthStencilAttachment must meet the GPURenderPassDepthStencilAttachmentDescriptor Valid Usage rules.

  5. Each attachment in this.colorAttachments and this.depthStencilAttachment.attachment, if present, must have all have the same [[sampleCount]].

  6. The dimensions of the subresources seen by each attachment in this.colorAttachments and this.depthStencilAttachment.attachment, if present, must match.

Define maximum color attachments

support for no attachments <https://github.com/gpuweb/gpuweb/issues/503>

15.1.1.1. Color Attachments
dictionary GPURenderPassColorAttachmentDescriptor {
    required GPUTextureView attachment;
    GPUTextureView resolveTarget;

    required (GPULoadOp or GPUColor) loadValue;
    GPUStoreOp storeOp = "store";
};
attachment, of type GPUTextureView

A GPUTextureView describing the texture subresource that will be output to for this color attachment.

resolveTarget, of type GPUTextureView

A GPUTextureView describing the texture subresource that will receive the resolved output for this color attachment if attachment is multisampled.

loadValue, of type (GPULoadOp or GPUColor)

If a GPULoadOp, indicates the load operation to perform on attachment prior to executing the render pass. If a GPUColor, indicates the value to clear attachment to prior to executing the render pass.

storeOp, of type GPUStoreOp, defaulting to "store"

The store operation to perform on attachment after executing the render pass.

GPURenderPassColorAttachmentDescriptor Valid Usage

Given a GPURenderPassColorAttachmentDescriptor this the following validation rules apply:

  1. this.attachment must have a renderable color format.

  2. this.attachment.[[texture]].[[textureUsage]] must contain OUTPUT_ATTACHMENT.

  3. this.attachment must be a view of a single subresource.

  4. If this.resolveTarget is not null:

    1. this.attachment must be multisampled.

    2. this.resolveTarget must not be multisampled.

    3. this.resolveTarget.[[texture]].[[textureUsage]] must contain OUTPUT_ATTACHMENT.

    4. this.resolveTarget must be a view of a single subresource.

    5. The dimensions of the subresources seen by this.resolveTarget and this.attachment must match.

    6. this.resolveTarget.[[texture]].[[format]] must match this.attachment.[[texture]].[[format]].

    7. Describe any remaining resolveTarget validation

Describe the remaining validation rules for this type.

15.1.1.2. Depth/Stencil Attachments
dictionary GPURenderPassDepthStencilAttachmentDescriptor {
    required GPUTextureView attachment;

    required (GPULoadOp or float) depthLoadValue;
    required GPUStoreOp depthStoreOp;
    boolean depthReadOnly = false;

    required (GPULoadOp or GPUStencilValue) stencilLoadValue;
    required GPUStoreOp stencilStoreOp;
    boolean stencilReadOnly = false;
};
attachment, of type GPUTextureView

A GPUTextureView describing the texture subresource that will be output to and read from for this depth/stencil attachment.

depthLoadValue, of type (GPULoadOp or float)

If a GPULoadOp, indicates the load operation to perform on attachment's depth component prior to executing the render pass. If a float, indicates the value to clear attachment's depth component to prior to executing the render pass.

depthStoreOp, of type GPUStoreOp

The store operation to perform on attachment's depth component after executing the render pass.

depthReadOnly, of type boolean, defaulting to false

Indicates that the depth component of attachment is read only.

stencilLoadValue, of type (GPULoadOp or GPUStencilValue)

If a GPULoadOp, indicates the load operation to perform on attachment's stencil component prior to executing the render pass. If a GPUStencilValue, indicates the value to clear attachment's stencil component to prior to executing the render pass.

stencilStoreOp, of type GPUStoreOp

The store operation to perform on attachment's stencil component after executing the render pass.

stencilReadOnly, of type boolean, defaulting to false

Indicates that the stencil component of attachment is read only.

GPURenderPassDepthStencilAttachmentDescriptor Valid Usage

Given a GPURenderPassDepthStencilAttachmentDescriptor this the following validation rules apply:

  1. this.attachment must have a renderable depth-and/or-stencil format.

  2. this.attachment must be a view of a single texture subresource.

  3. this.attachment.[[textureUsage]] must contain OUTPUT_ATTACHMENT.

  4. this.depthReadOnly is true, this.depthLoadValue must be "load" and this.depthStoreOp must be "store".

  5. this.stencilReadOnly is true, this.stencilLoadValue must be "load" and this.stencilStoreOp must be "store".

Describe the remaining validation rules for this type.

15.1.1.3. Load & Store Operations
enum GPULoadOp {
    "load"
};
enum GPUStoreOp {
    "store",
    "clear"
};

15.1.2. Drawing

setPipeline(pipeline)

Sets the current GPURenderPipeline.

Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.setPipeline(pipeline) method.
Parameter Type Nullable Optional Description
pipeline GPURenderPipeline The render pipeline to use for subsequent drawing commands.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

    Validate that pipeline is compatible with the render pass descriptor.

  2. Set this.[[pipeline]] to be pipeline.

setIndexBuffer(buffer, indexFormat, offset, size)

Sets the current index buffer.

Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.setIndexBuffer(buffer, indexFormat, offset, size) method.
Parameter Type Nullable Optional Description
buffer GPUBuffer Buffer containing index data to use for subsequent drawing commands.
indexFormat GPUIndexFormat Format of the index data contained in buffer.
offset GPUSize64 Offset in bytes into buffer where the index data begins.
size GPUSize64 Size in bytes of the index data in buffer. If 0, buffer.[[size]] - offset is used.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Add buffer to the usage scope as input.

  3. Set this.[[index_buffer]] to be buffer.

  4. Set this.[[index_format]] to be indexFormat.

setVertexBuffer(slot, buffer, offset, size)

Sets the current vertex buffer for the given slot.

Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.setVertexBuffer(slot, buffer, offset, size) method.
Parameter Type Nullable Optional Description
slot GPUIndex32 The vertex buffer slot to set the vertex buffer for.
buffer GPUBuffer Buffer containing vertex data to use for subsequent drawing commands.
offset GPUSize64 Offset in bytes into buffer where the vertex data begins.
size GPUSize64 Size in bytes of the vertex data in buffer. If 0, buffer.[[size]] - offset is used.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

    Define the maximum number of vertex buffers.

  2. Add buffer to the usage scope as input.

  3. Set this.[[vertex_buffers]][slot] to be buffer.

draw(vertexCount, instanceCount, firstVertex, firstInstance)

Draws primitives.

Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.draw(vertexCount, instanceCount, firstVertex, firstInstance) method.
Parameter Type Nullable Optional Description
vertexCount GPUSize32 The number of vertices to draw.
instanceCount GPUSize32 The number of instances to draw.
firstVertex GPUSize32 Offset into the vertex buffers, in vertices, to begin drawing from.
firstInstance GPUSize32 First instance to draw.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

If any of the following conditions are unsatisfied, make this invalid and stop.
drawIndexed(indexCount, instanceCount, firstIndex, baseVertex, firstInstance)

Draws indexed primitives.

Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.drawIndexed(indexCount, instanceCount, firstIndex, baseVertex, firstInstance) method.
Parameter Type Nullable Optional Description
indexCount GPUSize32 The number of indices to draw.
instanceCount GPUSize32 The number of instances to draw.
firstIndex GPUSize32 Offset into the index buffer, in indices, begin drawing from.
baseVertex GPUSignedOffset32 Added to each index value before indexing into the vertex buffers.
firstInstance GPUSize32 First instance to draw.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

If any of the following conditions are unsatisfied, make this invalid and stop.
drawIndirect(indirectBuffer, indirectOffset)

Draws primitives using parameters read from a GPUBuffer.

The indirect draw parameters encoded in the buffer must be a tightly packed block of four 32-bit unsigned integer values (16 bytes total), given in the same order as the arguments for draw(). For example:

        let drawIndirectParameters = new Uint32Array(4);
        drawIndirectParameters[0] = vertexCount;
        drawIndirectParameters[1] = instanceCount;
        drawIndirectParameters[2] = firstVertex;
        drawIndirectParameters[3] = firstInstance;
Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.drawIndirect(indirectBuffer, indirectOffset) method.
Parameter Type Nullable Optional Description
indirectBuffer GPUBuffer Buffer containing the indirect draw parameters.
indirectOffset GPUSize64 Offset in bytes into indirectBuffer where the drawing data begins.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Add indirectBuffer to the usage scope as input.

drawIndexedIndirect(indirectBuffer, indirectOffset)

Draws indexed primitives using parameters read from a GPUBuffer.

The indirect drawIndexed parameters encoded in the buffer must be a tightly packed block of five 32-bit unsigned integer values (20 bytes total), given in the same order as the arguments for drawIndexed(). For example:

        let drawIndexedIndirectParameters = new Uint32Array(5);
        drawIndexedIndirectParameters[0] = indexCount;
        drawIndexedIndirectParameters[1] = instanceCount;
        drawIndexedIndirectParameters[2] = firstIndex;
        drawIndexedIndirectParameters[3] = baseVertex;
        drawIndexedIndirectParameters[4] = firstInstance;
Called on: GPURenderEncoderBase this.

Arguments:

Arguments for the GPURenderEncoderBase.drawIndexedIndirect(indirectBuffer, indirectOffset) method.
Parameter Type Nullable Optional Description
indirectBuffer GPUBuffer Buffer containing the indirect drawIndexed parameters.
indirectOffset GPUSize64 Offset in bytes into indirectBuffer where the drawing data begins.

Returns: undefined

Issue the following steps on the Device timeline of this.[[device]]:

  1. If any of the following conditions are unsatisfied, make this invalid and stop.

  2. Add indirectBuffer to the usage scope as input.

To determine if it’s valid to draw with GPURenderEncoderBase encoder run the following steps:

If any of the following conditions are unsatisfied, return false:

Otherwise return true.

To determine if it’s valid to draw indexed with GPURenderEncoderBase encoder run the following steps:

If any of the following conditions are unsatisfied, return false:

Otherwise return true.

15.1.3. Rasterization state

The GPURenderPassEncoder has several methods which affect how draw commands are rasterized to attachments used by this encoder.

setViewport(x, y, width, height, minDepth, maxDepth)

Sets the viewport used during the rasterization stage to linearly map from normalized device coordinates to viewport coordinates.

Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.setViewport(x, y, width, height, minDepth, maxDepth) method.
Parameter Type Nullable Optional Description
x float Minimum X value of the viewport in pixels.
y float Minimum Y value of the viewport in pixels.
width float Width of the viewport in pixels.
height float Height of the viewport in pixels.
minDepth float Minimum depth value of the viewport.
maxDepth float Maximum depth value of the viewport.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    • width is greater than 0.

    • height is greater than 0.

    • minDepth is greater than or equal to 0.0 and less than or equal to 1.0.

    • maxDepth is greater than or equal to 0.0 and less than or equal to 1.0.

  2. Set the viewport to the extents x, y, width, height, minDepth, and maxDepth.

Allowed for GPUs to use fixed point or rounded viewport coordinates

setScissorRect(x, y, width, height)

Sets the scissor rectangle used during the rasterization stage. After transformation into viewport coordinates any fragments which fall outside the scissor rectangle will be discarded.

Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.setScissorRect(x, y, width, height) method.
Parameter Type Nullable Optional Description
x GPUIntegerCoordinate Minimum X value of the scissor rectangle in pixels.
y GPUIntegerCoordinate Minimum Y value of the scissor rectangle in pixels.
width GPUIntegerCoordinate Width of the scissor rectangle in pixels.
height GPUIntegerCoordinate Height of the scissor rectangle in pixels.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    • x is greater than or equal to 0.

    • y is greater than or equal to 0.

    • width is greater than 0.

    • height is greater than 0.

    • x+width is less than or equal to this.[[attachment_size]].width.

    • y+height is less than or equal to this.[[attachment_size]].height.

  2. Set the scissor rectangle to the extents x, y, width, and height.

setBlendColor(color)

Sets the constant blend color and alpha values used with "blend-color" and "one-minus-blend-color" GPUBlendFactors.

Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.setBlendColor(color) method.
Parameter Type Nullable Optional Description
color GPUColor The color to use when blending.
setStencilReference(reference)

Sets the stencil reference value used during stencil tests with the the "replace" GPUStencilOperation.

Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.setStencilReference(reference) method.
Parameter Type Nullable Optional Description
reference GPUStencilValue The stencil reference value.

15.1.4. Queries

beginOcclusionQuery(queryIndex)
Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.beginOcclusionQuery(queryIndex) method.
Parameter Type Nullable Optional Description
queryIndex GPUSize32

Returns: undefined

Describe beginOcclusionQuery() algorithm steps.

endOcclusionQuery()
Called on: GPURenderPassEncoder this.

Returns: undefined

Describe endOcclusionQuery() algorithm steps.

beginPipelineStatisticsQuery(querySet, queryIndex)
Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.beginPipelineStatisticsQuery(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

Describe beginPipelineStatisticsQuery() algorithm steps.

endPipelineStatisticsQuery()
Called on: GPURenderPassEncoder this.

Returns: undefined

Describe endPipelineStatisticsQuery() algorithm steps.

writeTimestamp(querySet, queryIndex)
Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.writeTimestamp(querySet, queryIndex) method.
Parameter Type Nullable Optional Description
querySet GPUQuerySet
queryIndex GPUSize32

Returns: undefined

Describe writeTimestamp() algorithm steps.

15.1.5. Bundles

executeBundles(bundles)

Executes the commands previously recorded into the given GPURenderBundles as part of this render pass.

When a GPURenderBundle is executed, it does not inherit the render pass’s pipeline, bind groups, or vertex and index buffers. After a GPURenderBundle has executed, the render pass’s pipeline, bind groups, and vertex and index buffers are cleared. If zero GPURenderBundles are executed, the command buffer state is unchanged.

Called on: GPURenderPassEncoder this.

Arguments:

Arguments for the GPURenderPassEncoder.executeBundles(bundles) method.
Parameter Type Nullable Optional Description
bundles sequence<GPURenderBundle> List of render bundles to execute.

Returns: undefined

Describe executeBundles() algorithm steps.

15.1.6. Finalization

The render pass encoder can be ended by calling endPass() once the user has finished recording commands for the pass. Once endPass() has been called the render pass encoder can no longer be used.

endPass()

Completes recording of the render pass commands sequence.

Called on: GPURenderPassEncoder this.

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    Add remaining validation.

Enqueue the attachment stores (with storeOp clear).

16. Bundles

16.1. GPURenderBundle

interface GPURenderBundle {
};
GPURenderBundle includes GPUObjectBase;

16.1.1. Creation

dictionary GPURenderBundleDescriptor : GPUObjectDescriptorBase {
};
interface GPURenderBundleEncoder {
    GPURenderBundle finish(optional GPURenderBundleDescriptor descriptor = {});
};
GPURenderBundleEncoder includes GPUObjectBase;
GPURenderBundleEncoder includes GPUProgrammablePassEncoder;
GPURenderBundleEncoder includes GPURenderEncoderBase;
createRenderBundleEncoder(descriptor)

Creates a GPURenderBundleEncoder.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createRenderBundleEncoder(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderBundleEncoderDescriptor Description of the GPURenderBundleEncoder to create.

Returns: GPURenderBundleEncoder

Describe createRenderBundleEncoder() algorithm steps.

16.1.2. Encoding

dictionary GPURenderBundleEncoderDescriptor : GPUObjectDescriptorBase {
    required sequence<GPUTextureFormat> colorFormats;
    GPUTextureFormat depthStencilFormat;
    GPUSize32 sampleCount = 1;
};

16.1.3. Finalization

finish(descriptor)

Completes recording of the render bundle commands sequence.

Called on: GPURenderBundleEncoder this.

Arguments:

Arguments for the GPURenderBundleEncoder.finish(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPURenderBundleDescriptor

Returns: GPURenderBundle

Describe finish() algorithm steps.

17. Queues

interface GPUQueue {
    undefined submit(sequence<GPUCommandBuffer> commandBuffers);

    GPUFence createFence(optional GPUFenceDescriptor descriptor = {});
    undefined signal(GPUFence fence, GPUFenceValue signalValue);

    undefined writeBuffer(
        GPUBuffer buffer,
        GPUSize64 bufferOffset,
        [AllowShared] BufferSource data,
        optional GPUSize64 dataOffset = 0,
        optional GPUSize64 size);

    undefined writeTexture(
      GPUTextureCopyView destination,
      [AllowShared] BufferSource data,
      GPUTextureDataLayout dataLayout,
      GPUExtent3D size);

    undefined copyImageBitmapToTexture(
        GPUImageBitmapCopyView source,
        GPUTextureCopyView destination,
        GPUExtent3D copySize);
};
GPUQueue includes GPUObjectBase;

GPUQueue has the following methods:

writeBuffer(buffer, bufferOffset, data, dataOffset, size)

Issues a write operation of the provided data into a GPUBuffer.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.writeBuffer(buffer, bufferOffset, data, dataOffset, size) method.
Parameter Type Nullable Optional Description
buffer GPUBuffer The buffer to write to.
bufferOffset GPUSize64 Offset in bytes into buffer to begin writing at.
data BufferSource Data to write into buffer.
dataOffset GPUSize64 Offset in into data to begin writing from. Given in elements if data is a TypedArray and bytes otherwise.
size GPUSize64 Size of content to write from data to buffer. Given in elements if data is a TypedArray and bytes otherwise.

Returns: undefined

  1. If data is an ArrayBuffer or DataView, let the element type be "byte". Otherwise, data is a TypedArray; let the element type be the type of the TypedArray.

  2. Let dataSize be the size of data, in elements.

  3. If size is unspecified, let contentsSize be dataSizedataOffset. Otherwise, let contentsSize be size.

  4. If any of the following conditions are unsatisfied, throw OperationError and stop.

    • contentsSize ≥ 0.

    • dataOffset + contentsSizedataSize.

    • contentsSize, converted to bytes, is a multiple of 4 bytes.

  5. Let dataContents be a copy of the bytes held by the buffer source.

  6. Let contents be the contentsSize elements of dataContents starting at an offset of dataOffset elements.

  7. Issue the following steps on the Queue timeline of this:

    1. If any of the following conditions are unsatisfied, generate a validation error and stop.

    2. Write contents into buffer starting at bufferOffset.

writeTexture(destination, data, dataLayout, size)

Issues a write operation of the provided data into a GPUTexture.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.writeTexture(destination, data, dataLayout, size) method.
Parameter Type Nullable Optional Description
destination GPUTextureCopyView The texture subresource and origin to write to.
data BufferSource Data to write into destination.
dataLayout GPUTextureDataLayout Layout of the content in data.
size GPUExtent3D Extents of the content to write from data to destination.

Returns: undefined

  1. Let dataBytes be a copy of the bytes held by the buffer source data.

  2. Let dataByteSize be the number of bytes in dataBytes.

  3. If any of the following conditions are unsatisfied, throw OperationError and stop.

  4. Let contents be the contents of the images seen by viewing dataBytes with dataLayout and size.

    Specify more formally.

  5. Issue the following steps on the Queue timeline of this:

    1. If any of the following conditions are unsatisfied, generate a validation error and stop.

      Note: unlike GPUCommandEncoder.copyBufferToTexture(), there is no alignment requirement on dataLayout.bytesPerRow.

    2. Write contents into destination.

      Specify more formally.

copyImageBitmapToTexture(source, destination, copySize)

Schedules a copy operation of the contents of an image bitmap into the destination texture.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.copyImageBitmapToTexture(source, destination, copySize) method.
Parameter Type Nullable Optional Description
source GPUImageBitmapCopyView ImageBitmap and origin to copy to destination.
destination GPUTextureCopyView The texture subresource and origin to write to.
copySize GPUExtent3D Extents of the content to write from source to destination.

Returns: undefined

If any of the following conditions are unsatisfied, throw an OperationError and stop.

submit(commandBuffers)

Schedules the execution of the command buffers by the GPU on this queue.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.submit(commandBuffers) method.
Parameter Type Nullable Optional Description
commandBuffers sequence<GPUCommandBuffer>

Returns: undefined

Issue the following steps on the Device timeline of this:

  1. If any of the following conditions are unsatisfied, generate a validation error and stop.

  2. Issue the following steps on the Queue timeline of this:

    1. For each commandBuffer in commandBuffers:

      1. Execute each command in commandBuffer.[[command_list]].

17.1. GPUFence

interface GPUFence {
    GPUFenceValue getCompletedValue();
    Promise<undefined> onCompletion(GPUFenceValue completionValue);
};
GPUFence includes GPUObjectBase;

17.1.1. Creation

dictionary GPUFenceDescriptor : GPUObjectDescriptorBase {
    GPUFenceValue initialValue = 0;
};
createFence(descriptor)

Creates a GPUFence.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.createFence(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUFenceDescriptor Description of the GPUFence to create.

Returns: GPUFence

Describe createFence() algorithm steps.

17.1.2. Completion

Completion of a fence is signaled from the GPUQueue that created it.

signal(fence, signalValue)

Signals the given fence, increasing it’s completed value to signalValue.

Called on: GPUQueue this.

Arguments:

Arguments for the GPUQueue.signal(fence, signalValue) method.
Parameter Type Nullable Optional Description
fence GPUFence The fence to signal.
signalValue GPUFenceValue The value to increase fence’s completion value to.

Returns: undefined

Describe signal() algorithm steps.

The completion of the fence and the value it completes with can be observed from the GPUFence.

getCompletedValue()

Returns the largest signalled value completion value for the fence that has propagated to the content timeline.

Called on: GPUFence this.

Returns: GPUFenceValue

Describe getCompletedValue() algorithm steps.

onCompletion(completionValue)

Returns a Promise that resolves once the fence’s completion value ≥ completionValue.

Called on: GPUFence this.

Arguments:

Arguments for the GPUFence.onCompletion(completionValue) method.
Parameter Type Nullable Optional Description
completionValue GPUFenceValue The completion value that the fence must meet or exceed before resolving the returned Promise

Returns: Promise<undefined>

Describe onCompletion() algorithm steps.

18. Queries

18.1. GPUQuerySet

interface GPUQuerySet {
    undefined destroy();
};
GPUQuerySet includes GPUObjectBase;

18.1.1. Creation

dictionary GPUQuerySetDescriptor : GPUObjectDescriptorBase {
    required GPUQueryType type;
    required GPUSize32 count;
    sequence<GPUPipelineStatisticName> pipelineStatistics = [];
};
pipelineStatistics, of type sequence<GPUPipelineStatisticName>, defaulting to []

The set of GPUPipelineStatisticName values in this sequence defines which pipeline statistics will be returned in the new query set.

Valid Usage
  1. pipelineStatistics is ignored if type is not pipeline-statistics.

  2. If pipeline-statistics-query is not available, type must not be pipeline-statistics.

  3. If type is pipeline-statistics, pipelineStatistics must be a sequence of GPUPipelineStatisticName values which cannot be duplicated.

createQuerySet(descriptor)

Creates a GPUQuerySet.

Called on: GPUDevice this.

Arguments:

Arguments for the GPUDevice.createQuerySet(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUQuerySetDescriptor Description of the GPUQuerySet to create.

Returns: GPUQuerySet

Describe createQuerySet() algorithm steps.

18.1.2. Finalization

destroy()

Destroys the GPUQuerySet.

Called on: GPUQuerySet this.

Returns: undefined

Describe destroy() algorithm steps.

18.2. QueryType

enum GPUQueryType {
    "occlusion",
    "pipeline-statistics",
    "timestamp"
};

18.3. Pipeline Statistics Query

enum GPUPipelineStatisticName {
    "vertex-shader-invocations",
    "clipper-invocations",
    "clipper-primitives-out",
    "fragment-shader-invocations",
    "compute-shader-invocations"
};

When resolving pipeline statistics query, each result is written into GPUSize64, and the number and order of the results written to GPU buffer matches the number and order of GPUPipelineStatisticName specified in pipelineStatistics.

The beginPipelineStatisticsQuery() and endPipelineStatisticsQuery() (on both GPUComputePassEncoder and GPURenderPassEncoder) cannot be nested. A pipeline statistics query must be ended before beginning another one.

Pipeline statistics query requires pipeline-statistics-query is available on the device.

18.4. Timestamp Query

Timestamp query allows application to write timestamp values to a GPUQuerySet by calling writeTimestamp() on GPUComputePassEncoder or GPURenderPassEncoder or GPUCommandEncoder, and then resolve timestamp values in nanoseconds (type of GPUSize64) to a GPUBuffer (using resolveQuerySet()).

Timestamp query requires timestamp-query is available on the device.

Note: The timestamp values may be zero if the physical device reset timestamp counter, please ignore it and the following values.

Write normative text about timestamp value resets.

Because timestamp query provides high-resolution GPU timestamp, we need to decide what constraints, if any, are on its availability.

19. Canvas Rendering & Swap Chains

interface GPUCanvasContext {
    GPUSwapChain configureSwapChain(GPUSwapChainDescriptor descriptor);

    Promise<GPUTextureFormat> getSwapChainPreferredFormat(GPUDevice device);
};
configureSwapChain(descriptor)

Configures the swap chain for this canvas, and returns a new GPUSwapChain object representing it. Destroys any swapchain previously returned by configureSwapChain, including all of the textures it has produced.

Called on: GPUCanvasContext this.

Arguments:

Arguments for the GPUCanvasContext.configureSwapChain(descriptor) method.
Parameter Type Nullable Optional Description
descriptor GPUSwapChainDescriptor Description of the GPUSwapChain to configure.

Returns: GPUSwapChain

Describe configureSwapChain() algorithm steps.

getSwapChainPreferredFormat(device)

Returns an optimal GPUTextureFormat to use for swap chains with this context and the given device.

Called on: GPUCanvasContext this.

Arguments:

Arguments for the GPUCanvasContext.getSwapChainPreferredFormat(device) method.
Parameter Type Nullable Optional Description
device GPUDevice Device the swap chain format should be queried for.

Returns: Promise<GPUTextureFormat>

Describe getSwapChainPreferredFormat() algorithm steps.

dictionary GPUSwapChainDescriptor : GPUObjectDescriptorBase {
    required GPUDevice device;
    required GPUTextureFormat format;
    GPUTextureUsageFlags usage = 0x10;  // GPUTextureUsage.OUTPUT_ATTACHMENT
};
interface GPUSwapChain {
    GPUTexture getCurrentTexture();
};
GPUSwapChain includes GPUObjectBase;

In the "update the rendering [of the] Document" step of the "Update the rendering" HTML processing model, the contents of the GPUTexture most recently returned by getCurrentTexture() are used to update the rendering for the canvas, and it is as if destroy() were called on it (making it unusable elsewhere in WebGPU).

Before this drawing buffer is presented for compositing, the implementation shall ensure that all rendering operations have been flushed to the drawing buffer.

getCurrentTexture()

Get the GPUTexture that will be composited to the document by the GPUCanvasContext that created this swap chain next.

Called on: GPUSwapChain this.

Returns: GPUTexture

Describe getCurrentTexture() algorithm steps.

20. Errors & Debugging

20.1. Fatal Errors

interface GPUDeviceLostInfo {
    readonly attribute DOMString message;
};

partial interface GPUDevice {
    readonly attribute Promise<GPUDeviceLostInfo> lost;
};

20.2. Error Scopes

enum GPUErrorFilter {
    "out-of-memory",
    "validation"
};
interface GPUOutOfMemoryError {
    constructor();
};

interface GPUValidationError {
    constructor(DOMString message);
    readonly attribute DOMString message;
};

typedef (GPUOutOfMemoryError or GPUValidationError) GPUError;
partial interface GPUDevice {
    undefined pushErrorScope(GPUErrorFilter filter);
    Promise<GPUError?> popErrorScope();
};
pushErrorScope(filter)

Define pushErrorScope.

popErrorScope()

Define popErrorScope.

Rejects with OperationError if:

  • The device is lost.

  • There are no error scopes on the stack.

20.3. Telemetry

[
    Exposed=(Window, DedicatedWorker)
]
interface GPUUncapturedErrorEvent : Event {
    constructor(
        DOMString type,
        GPUUncapturedErrorEventInit gpuUncapturedErrorEventInitDict
    );
    [SameObject] readonly attribute GPUError error;
};

dictionary GPUUncapturedErrorEventInit : EventInit {
    required GPUError error;
};
partial interface GPUDevice {
    [Exposed=(Window, DedicatedWorker)]
    attribute EventHandler onuncapturederror;
};

21. Type Definitions

typedef [EnforceRange] unsigned long GPUBufferDynamicOffset;
typedef [EnforceRange] unsigned long long GPUFenceValue;
typedef [EnforceRange] unsigned long GPUStencilValue;
typedef [EnforceRange] unsigned long GPUSampleMask;
typedef [EnforceRange] long GPUDepthBias;

typedef [EnforceRange] unsigned long long GPUSize64;
typedef [EnforceRange] unsigned long GPUIntegerCoordinate;
typedef [EnforceRange] unsigned long GPUIndex32;
typedef [EnforceRange] unsigned long GPUSize32;
typedef [EnforceRange] long GPUSignedOffset32;

typedef unsigned long GPUFlagsConstant;

21.1. Colors & Vectors

dictionary GPUColorDict {
    required double r;
    required double g;
    required double b;
    required double a;
};
typedef (sequence<double> or GPUColorDict) GPUColor;

Note: double is large enough to precisely hold 32-bit signed/unsigned integers and single-precision floats.

dictionary GPUOrigin2DDict {
    GPUIntegerCoordinate x = 0;
    GPUIntegerCoordinate y = 0;
};
typedef (sequence<GPUIntegerCoordinate> or GPUOrigin2DDict) GPUOrigin2D;
dictionary GPUOrigin3DDict {
    GPUIntegerCoordinate x = 0;
    GPUIntegerCoordinate y = 0;
    GPUIntegerCoordinate z = 0;
};
typedef (sequence<GPUIntegerCoordinate> or GPUOrigin3DDict) GPUOrigin3D;

An Origin3D is a